Automatic merge from submit-queue (batch tested with PRs 61803, 64305, 64170, 64361, 64339). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.
Add TLS support to exec authenticator plugin
**What this PR does / why we need it**:
https://github.com/kubernetes/community/blob/master/contributors/design-proposals/auth/kubectl-exec-plugins.md#tls-client-certificate-support
Allows exec plugin to return raw TLS key/cert data. This data populates
transport.Config.TLS field.
This requires a change to AuthProvider interface to expose TLS configs,
not only RoundTripper.
**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes#61421
**Special notes for your reviewer**:
**Release note**:
```release-note
Exec authenticator plugin supports TLS client certificates.
```
Kubernetes-commit: f701b7529937493a64f2f2553aa9a5cd7020d9b7
