Fix RBAC cluster/rolebinding subjects and SA namespace empty check

[astraw99]

What type of PR is this?

/kind bug

What this PR does / why we need it:

Add subjects and namespace empty check in RBAC cluster/rolebinding.
Also add some test cases.

Which issue(s) this PR fixes:

Fixes #129265

Does this PR introduce a user-facing change?

NONE

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[googs1025]

/retest

[k8s-ci-robot]

@astraw99: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-kubernetes-integration	d967ddc	link	true	/test pull-kubernetes-integration
pull-kubernetes-e2e-kind	d967ddc	link	true	/test pull-kubernetes-e2e-kind
pull-kubernetes-conformance-kind-ga-only-parallel	d967ddc	link	true	/test pull-kubernetes-conformance-kind-ga-only-parallel
pull-kubernetes-e2e-kind-ipv6	d967ddc	link	true	/test pull-kubernetes-e2e-kind-ipv6
pull-kubernetes-verify	d967ddc	link	true	/test pull-kubernetes-verify
pull-kubernetes-e2e-gce	d967ddc	link	true	/test pull-kubernetes-e2e-gce

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[enj]

Thanks for the PR. However, tightening validation is not allowed as it is backward incompatible.

Empty namespace means "use the same namespace as the role binding."

Empty subject lists are used by some controllers to make it easier to dynamically add and remove items from the list without having to delete the binding when the list is empty.

/close

[k8s-ci-robot]

@enj: Closed this PR.

In response to this:

Thanks for the PR. However, tightening validation is not allowed as it is backward incompatible.

Empty namespace means "use the same namespace as the role binding."

Empty subject lists are used by some controllers to make it easier to dynamically add and remove items from the list without having to delete the binding when the list is empty.

/close

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