Backport of xds: return errors from public listener finalization into release/2.0.x

[hc-github-team-consul-core]

Backport

This PR is auto-generated from #23686 to be assessed for backporting due to the inclusion of the label backport/2.0.

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@Surabhi-1605
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The below text is copied from the body of the original PR.

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finalizePublicListenerFromConfig previously returned nil when injecting the
L4 intention (RBAC) filter or the mTLS transport socket failed, so the caller's
error handling never triggered. This returns the error from both paths so an inbound
public listener is dropped rather than served without intention enforcement or mTLS.

Adds TestFinalizePublicListenerFromConfig_PropagatesInjectionErrors, which fails
if either error is swallowed again.

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Overview of commits

• d805469

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