[k8s] Realtime GPU availability of kubernetes cluster in `sky show-gpus` #14777

Job	Run time
python-test (3.8, tests/unit_tests)	6m 18s
python-test (3.8, tests/test_api.py)	3m 50s
python-test (3.8, tests/test_cli.py)	3m 59s
python-test (3.8, tests/test_config.py)	3m 47s
python-test (3.8, tests/test_global_user_state.py)	3m 41s
python-test (3.8, tests/test_jobs.py)	4m 16s
python-test (3.8, tests/test_list_accelerators.py)	4m 4s
python-test (3.8, tests/test_optimizer_dryruns.py)	5m 29s
python-test (3.8, tests/test_optimizer_random_dag.py)	4m 26s
python-test (3.8, tests/test_storage.py)	3m 37s
python-test (3.8, tests/test_wheels.py)	3m 53s
python-test (3.8, tests/test_jobs_and_serve.py)	3m 44s
python-test (3.8, tests/test_yaml_parser.py)	3m 42s
	54m 46s

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