E2E tests for startup probe

[mgencur]

Additional tests for startup probes.

Proposed Changes

• Verify startup probes can be used on sidecars.
• Verify different types of startup probes can be used (TCPSocket, HTTPGet, GRPC)
• Verify a liveness probe being aware of a startup probe. The liveness probe can only start after the startup probe succeeds.

Release Note

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Project coverage is 84.46%. Comparing base (6554a7d) to head (78ca7fa).

Files	Patch %	Lines
pkg/testing/v1/service.go	0.00%	3 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #15461 +/- ## ========================================== - Coverage 84.48% 84.46% -0.02% ========================================== Files 219 219 Lines 13605 13608 +3 ========================================== Hits 11494 11494 - Misses 1740 1743 +3 Partials 371 371 ```

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[knative-prow[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: mgencur, ReToCode

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