SLO burnRate rule should indicate user error when SLO itself is not found #230128
Description
We've seen versions of this message in our logs:
Executing Rule {{space}}:slo.rules.burnRate:{{rule-id}} has resulted in Error:
SLO [{{slo-id}}] not found - SLONotFound: SLO [{{slo-id}}] not found
at KibanaSavedObjectsSLORepository.findById (@kbn/slo-plugin/server/services/slo_repository.js:53:13)
at Object.executor (@kbn/slo-plugin/server/lib/rules/slo_burn_rate/executor.js:51:15)
...
This error is flagged as a framework error, but should be flagged as a user error.