Set k8s default container label

[konstfish]

Fixes #15391

Proposed Changes

• Add the kubectl.kubernetes.io/default-container annotation to Pods, pointing to the user-container. This ensures kubectl will always select the correct container by default when interacting with kubectl logs, kubectl exec, etc.

Release Note

Add default container annotation to Pods created by the reconciler

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: konstfish / name: David Fischer (cf0d7fc, f1540e2, f154801, f154ef9, f1547df, f154393, f1545d9, f154388, f154fed)

[knative-prow]

Welcome @konstfish! It looks like this is your first PR to knative/serving 🎉

[knative-prow]

Hi @konstfish. Thanks for your PR.

I'm waiting for a knative member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[konstfish]

Some more notes on this, I was unsure if I should put this behind some sort of feature gate, but I'd be happy to as about ~12 tests were affected by these changes. Fix for now was just to include the extra annotation in the want (in https://github.com/knative/serving/pull/15694/files#diff-d93eacd83502ff2061608160378ff8c5c8b199fed97cd44e2b1ab73f419b9aab & https://github.com/knative/serving/pull/15694/files#diff-508e07fc6207ae8956d33f7753a1407b85885edff3135849635263501ed77fd5) but I feel like this isn't really the cleanest solution. Would love some feedback on that!

[dprotaso]

/ok-to-test

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.84%. Comparing base (dd48437) to head (f1547df).
Report is 9 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #15694      +/-   ##
==========================================
+ Coverage   80.81%   80.84%   +0.02%     
==========================================
  Files         222      222              
  Lines       18034    18035       +1     
==========================================
+ Hits        14574    14580       +6     
+ Misses       3088     3085       -3     
+ Partials      372      370       -2     

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[dprotaso]

looks good - one more minor change

[dprotaso]

/lgtm
/approve

thanks for the changes

[knative-prow]

[APPROVALNOTIFIER] This PR is APPROVED

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

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