test: Self-monitor webhook E2E test

[skhalash]

Description

Changes proposed in this pull request (what was done and why):

• Clean up existing self-monitor tests:
  • Remove irrelevant test cases
  • Remove a misleading verifier, the telemetry flow health check has to be added to the existing status verifier when the feature is released
  • Remove operational labels since we are not executing it in the upgrade job yet
  • Generate telemetry using telemetrygen
• Extend Prometheus matchers to be able to search for a metric with a specific key/label and a specific value
• Add a test to check if the webhook metric is incremented. Split metrics and traces self-monitor jobs, so they do not share the same manager instance and, thus, cannot influence the results of each other

Changes refer to particular issues, PRs or documents:

• Add webhook to trigger status reconciliations faster #903

Traceability

• The PR is linked to a GitHub issue.
• New features have a milestone set.
• New features have defined acceptance criteria in a corresponding GitHub Issue, and all criteria are satisfied with this PR.
• The corresponding GitHub issue has a respective area and kind label.
• The follow-up issues (if any) are linked in the Related Issues section.
• Adjusted the documentation if the change is user-facing.
• The feature is unit-tested
• The feature is e2e-tested

[kyma-bot]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all