feat: removes custom CPU and Memory usage Gauge

[simzzz]

Description

We used to rely on custom calculations, which may not be 100% accurate, to follow the CPU and Memory Usage of the WebSocket server.
Instead of having a custom collect function, we can use the process_cpu_seconds_total default metric for cpu and process_resident_memory_bytes for memory together with a rate function to get the percentage usage of cpu and memory.

This PR replaces custom gauges with existing default metrics (already enabled via collectDefaultMetrics()):

Related issue(s)

Fixes #3935

Testing Guide

1. Verify custom gauges have been removed from wsMetricRegistry.ts
2. Verify CPU/Memory gauge definitions have been removed from constants.ts
3. Once merged, verify the Grafana dashboard has been updated

Changes from original design (optional)

N/A

Additional work needed (optional)

N/A

Checklist

• I've assigned an assignee to this PR and related issue(s) (if applicable)
• I've assigned a label to this PR and related issue(s) (if applicable)
• I've assigned a milestone to this PR and related issue(s) (if applicable)
• I've updated documentation (code comments, README, etc. if applicable)
• I've done sufficient testing (unit, integration, etc.)

[github-actions]

Test Results

 20 files  ±0  265 suites  ±0   18m 31s ⏱️ +25s
712 tests ±0  707 ✅ +1  5 💤 ±0  0 ❌  - 1 
728 runs  ±0  723 ✅ +1  5 💤 ±0  0 ❌  - 1 

Results for commit 96f533a. ± Comparison against base commit cbf18eb.

♻️ This comment has been updated with latest results.

[quiet-node]

LGTM

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

@@            Coverage Diff             @@
##             main    #4176      +/-   ##
==========================================
+ Coverage   95.38%   95.56%   +0.17%     
==========================================
  Files         122      121       -1     
  Lines       20355    20220     -135     
  Branches     1737     1733       -4     
==========================================
- Hits        19416    19323      -93     
+ Misses        914      873      -41     
+ Partials       25       24       -1     

Flag	Coverage Δ
config-service	98.80% <ø> (ø)
relay	90.59% <ø> (-0.01%)	⬇️
server	89.35% <ø> (+0.22%)	⬆️
ws-server	53.73% <100.00%> (+0.10%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
packages/ws-server/src/metrics/wsMetricRegistry.ts	98.85% <100.00%> (+20.61%)	⬆️
packages/ws-server/src/utils/constants.ts	100.00% <100.00%> (ø)

... and 13 files with indirect coverage changes

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