[k8s] Exec auth support on k8s

[weih1121]

linked ticket: https://linear.app/skypilot/issue/SKY-959/[k8s]-support-exec-based-auth-kubeconfigs-on-controllers

Tested (run the relevant ones):

• Code formatting: bash format.sh
• Any manual or new tests for this PR (please specify below)
• All smoke tests: pytest tests/test_smoke.py
• Relevant individual smoke tests: pytest tests/test_smoke.py::test_fill_in_the_name
• Backward compatibility tests: conda deactivate; bash -i tests/backward_compatibility_tests.sh

[weih1121]

kubernetes:
  Syncing (to 1 node): /var/folders/d1/c810pqs51p58jyq4g4d8czbh0000gn/T/tmp5egq4o1h -> ~/.sky/managed_jobs/sky-ddb6-hong-9032.config_yaml
✓ Files synced.  View logs at: ~/sky_logs/sky-2025-01-08-19-02-48-871939/file_mounts.log
Auto-stop is not supported for Kubernetes and RunPod clusters. Skipping.
⚙︎ Job submitted, ID: 3
E0108 11:06:08.217324  282258 memcache.go:265] couldn't get current server API group list: Get "http://localhost:8080/api?timeout=32s": dial tcp 127.0.0.1:8080: connect: connection refused
E0108 11:06:08.218067  282258 memcache.go:265] couldn't get current server API group list: Get "http://localhost:8080/api?timeout=32s": dial tcp 127.0.0.1:8080: connect: connection refused
E0108 11:06:08.220005  282258 memcache.go:265] couldn't get current server API group list: Get "http://localhost:8080/api?timeout=32s": dial tcp 127.0.0.1:8080: connect: connection refused
E0108 11:06:08.220567  282258 memcache.go:265] couldn't get current server API group list: Get "http://localhost:8080/api?timeout=32s": dial tcp 127.0.0.1:8080: connect: connection refused
The connection to the server localhost:8080 was refused - did you specify the right host or port?
The job cluster is preempted or failed.
✓ Managed job finished: 3 (status: SUCCEEDED).

The output from the terminal caused by executing sudo kubectl get nodes whereas kubectl get nodes works successfully without sudo.
Check our codebase seems like it related to https://github.com/weih1121/skypilot/blob/885e5279daa3c52b933a796d82c3438b66772f6a/sky/provision/kubernetes/utils.py#L449. @romilbhardwaj @Michaelvll any suggestion?