[release-1.21] Add kubernetes registry in front of ServiceEntry

[istio-testing]

Manual cherrypick required.

#51003 failed to apply on top of branch "release-1.21":

Applying: add kubernetes registry infront of serviceentry
Applying: add test
Applying: add release note
Applying: address comments
Using index info to reconstruct a base tree...
M	pilot/pkg/serviceregistry/aggregate/controller.go
Falling back to patching base and 3-way merge...
Auto-merging pilot/pkg/serviceregistry/aggregate/controller.go
CONFLICT (content): Merge conflict in pilot/pkg/serviceregistry/aggregate/controller.go
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
Patch failed at 0004 address comments
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".