app/vmalert: rename samples to series (VictoriaMetrics#9204)

`Samples` could be confusing for users, especially for alerting rules:
* we say in docs that each returned "series" will create a new alert
* we say that there are "series fetched", so both columns should be
either "series" or "samples".

Let's rename it to `series` for consistency.

### Describe Your Changes

Please provide a brief description of the changes you made. Be as
specific as possible to help others understand the purpose and impact of
your modifications.

### Checklist

The following checks are **mandatory**:

- [ ] My change adheres to [VictoriaMetrics contributing
guidelines](https://docs.victoriametrics.com/victoriametrics/contributing/#pull-request-checklist).

---------

Signed-off-by: hagen1778 <roman@victoriametrics.com>

Author: hagen1778

app/vmalert/rule/alerting.go

@@ -416,7 +416,7 @@ func (ar *AlertingRule) exec(ctx context.Context, ts time.Time, limit int) ([]pr
 		return nil, fmt.Errorf("failed to execute query %q: %w", ar.Expr, err)
 	}
 
-	ar.logDebugf(ts, nil, "query returned %d samples (elapsed: %s, isPartial: %t)", curState.Samples, curState.Duration, isPartialResponse(res))
+	ar.logDebugf(ts, nil, "query returned %d series (elapsed: %s, isPartial: %t)", curState.Samples, curState.Duration, isPartialResponse(res))
 	qFn := func(query string) ([]datasource.Metric, error) {
 		res, _, err := ar.q.Query(ctx, query, ts)
 		return res.Data, err

app/vmalert/web.qtpl

@@ -162,7 +162,7 @@
                             <thead>
                                 <tr>
                                     <th scope="col" style="width: 60%">Rule</th>
-                                    <th scope="col" style="width: 20%" class="text-center" title="How many samples were produced by the rule">Samples</th>
+                                    <th scope="col" style="width: 20%" class="text-center" title="How many series were produced by the rule">Series</th>
                                     <th scope="col" style="width: 20%" class="text-center" title="How many seconds ago rule was executed">Updated</th>
                                 </tr>
                             </thead>
@@ -594,7 +594,7 @@
             <thead>
                 <tr>
                     <th scope="col" title="The time when event was created">Updated at</th>
-                    <th scope="col" style="width: 10%" class="text-center" title="How many samples were returned">Samples</th>
+                    <th scope="col" style="width: 10%" class="text-center" title="How many series expression returns. Each series will represent an alert.">Series returned</th>
                     {% if seriesFetchedEnabled %}<th scope="col" style="width: 10%" class="text-center" title="How many series were scanned by datasource during the evaluation">Series fetched</th>{% endif %}
                     <th scope="col" style="width: 10%" class="text-center" title="How many seconds request took">Duration</th>
                     <th scope="col" class="text-center" title="Time used for rule execution">Executed at</th>

app/vmalert/web.qtpl.go

@@ -905,19 +905,19 @@ Rows in the section represent ordered rule evaluations and their results.
 Every state has the following attributes:
 1. `Updated at` - the real time when this rule was executed by vmalert.
 1. `Executed at` - `time` param that was sent within the evaluation request to datasource.
-1. `Samples` - the amount of data samples returned during at this evaluation. Recording rule that has 0 samples produces
-    no results. Alerting rule that has 0 samples means `expr` condition is false and rule is in inactive state.
+1. `Series returned` - the amount of series returned during at this evaluation. Recording rule that has 0 series produces
+    no results. Alerting rule that has 0 series means `expr` condition is false and rule is in inactive state.
 1. `Series fetched` - the amount of series scanned during query evaluation. See [never-firing alerts](#never-firing-alerts).
 1. `Duration` - the time it took to evaluate the rule. If `Duration` is close or bigger to evaluation interval, then this
     rule can skip evaluations. See how to deal with [slow queries](https://docs.victoriametrics.com/victoriametrics/troubleshooting/#slow-queries). 
 1.  `cURL` - contains an example of HTTP request sent by vmalert to the `-datasource.url` during evaluation, including all extra headers and query params. 
     The command can be used for debugging purposes to see what vmalert receives in response from datasource. 
     _Sensitive info is stripped from the `curl` examples - see [security](#security) section for more details._
 
-If a specific state shows that there were **no samples returned** and executed **cURL command returns some data**,
+If a specific state shows that there were **no series returned** and executed **cURL command returns some data**,
 then it is likely there was no data in datasource on the moment when rule was evaluated. See about [data delay](#data-delay).
 
-vmalert exposes `vmalert_recording_rules_last_evaluation_samples` for recording rules to represent the amount of samples
+vmalert exposes `vmalert_recording_rules_last_evaluation_samples` for recording rules to represent the amount of series
 returned during evaluations. The following alerting rule can be used to detect those recording rules that produce no data:
 ```yaml
       - alert: RecordingRulesNoData
@@ -984,9 +984,9 @@ vmalert allows configuring more detailed logging for specific alerting or record
 Or for all rules within the [group](#groups) {{% available_from "v1.117.0" %}}.
 Just set `debug: true` in configuration and vmalert will start printing additional log messages:
 ```sh
-2022-09-15T13:35:41.155Z  DEBUG alerting rule "TestGroup":"Conns" (2601299393013563564) at 2022-09-15T15:35:41+02:00: query returned 0 samples (elapsed: 5.896041ms, isPartial: false)
+2022-09-15T13:35:41.155Z  DEBUG alerting rule "TestGroup":"Conns" (2601299393013563564) at 2022-09-15T15:35:41+02:00: query returned 0 series (elapsed: 5.896041ms, isPartial: false)
 2022-09-15T13:35:56.149Z  DEBUG datasource request: executing POST request with params "denyPartialResponse=true&query=sum%28vm_tcplistener_conns%7Binstance%3D%22localhost%3A8429%22%7D%29+by%28instance%29+%3E+0&step=15s&time=1663248945"
-2022-09-15T13:35:56.178Z  DEBUG alerting rule "TestGroup":"Conns" (2601299393013563564) at 2022-09-15T15:35:56+02:00: query returned 1 samples (elapsed: 28.368208ms, isPartial: false)
+2022-09-15T13:35:56.178Z  DEBUG alerting rule "TestGroup":"Conns" (2601299393013563564) at 2022-09-15T15:35:56+02:00: query returned 1 series (elapsed: 28.368208ms, isPartial: false)
 2022-09-15T13:35:56.178Z  DEBUG datasource request: executing POST request with params "denyPartialResponse=true&query=sum%28vm_tcplistener_conns%7Binstance%3D%22localhost%3A8429%22%7D%29&step=15s&time=1663248945"
 2022-09-15T13:35:56.179Z  DEBUG alerting rule "TestGroup":"Conns" (2601299393013563564) at 2022-09-15T15:35:56+02:00: alert 10705778000901301787 {alertgroup="TestGroup",alertname="Conns",cluster="east-1",instance="localhost:8429",replica="a"} created in state PENDING
 ...