Use istio.sidecar.inject label instead of annotation

[ReToCode]

Partially https://github.com/knative/serving/issues/15521

Proposed Changes

• Use istio.sidecar.inject label instead of annotation

/assign @skonto

[codecov[bot]]

Codecov Report

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

Project coverage is 78.45%. Comparing base (aabe552) to head (369cfcb). Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
test/crd.go	0.00%	3 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #3096 +/- ## ======================================= Coverage 78.45% 78.45% ======================================= Files 191 191 Lines 8938 8938 ======================================= Hits 7012 7012 Misses 1663 1663 Partials 263 263 ```

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[dprotaso]

/lgtm /approve

[knative-prow[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

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

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[dprotaso]

actually might need a follow up depending on the answer to this question:

https://github.com/knative-extensions/net-istio/pull/1369#issuecomment-2371351757