[Serve] Use safe_cursor for serve state

[Michaelvll]

I encourtered issues with service db locked, like the following

E 03-12 05:28:23 subprocess_utils.py:84]   File "<string>", line 1, in <module>
E 03-12 05:28:23 subprocess_utils.py:84]   File "/opt/conda/lib/python3.10/site-packages/sky/serve/serve_utils.py", line 451, in wait_service_registration
E 03-12 05:28:23 subprocess_utils.py:84]     record = serve_state.get_service_from_name(service_name)
E 03-12 05:28:23 subprocess_utils.py:84]   File "/opt/conda/lib/python3.10/site-packages/sky/serve/serve_state.py", line 311, in get_service_from_name
E 03-12 05:28:23 subprocess_utils.py:84]     rows = _DB.cursor.execute('SELECT * FROM services WHERE name=(?)',
E 03-12 05:28:23 subprocess_utils.py:84] sqlite3.OperationalError: database is locked

This PR adopts the safe_cursor we used for spot jobs to avoid the issue with best effort.

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: bash tests/backward_comaptibility_tests.sh