Add tests for Azure spot instance #18684

Job	Run time
python-test (3.8, tests/unit_tests)	3m 20s
python-test (3.8, tests/test_api.py)	38s
python-test (3.8, tests/test_cli.py)	59s
python-test (3.8, tests/test_config.py)	34s
python-test (3.8, tests/test_global_user_state.py)	28s
python-test (3.8, tests/test_jobs.py)	33s
python-test (3.8, tests/test_list_accelerators.py)	42s
python-test (3.8, tests/test_optimizer_dryruns.py)	1m 57s
python-test (3.8, tests/test_optimizer_random_dag.py)	1m 4s
python-test (3.8, tests/test_storage.py)	25s
python-test (3.8, tests/test_wheels.py)	32s
python-test (3.8, tests/test_jobs_and_serve.py)	30s
python-test (3.8, tests/test_yaml_parser.py)	25s
	12m 7s

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