[autoscaler v2] add test for node provider

[scv119]

Why are these changes needed?

add tests for node_provider v2 and refactor the mock code

Related issue number

Checks

• I've signed off every commit(by using the -s flag, i.e., git commit -s) in this PR.
• I've run scripts/format.sh to lint the changes in this PR.
• I've included any doc changes needed for https://docs.ray.io/en/master/.
  • I've added any new APIs to the API Reference. For example, if I added a
    method in Tune, I've added it in doc/source/tune/api/ under the
    corresponding .rst file.
• I've made sure the tests are passing. Note that there might be a few flaky tests, see the recent failures at https://flakey-tests.ray.io/
• Testing Strategy
  • Unit tests
  • Release tests
  • This PR is not tested :(

[rickyyx]

LGTM!

[rickyyx]

Some test failures look relevant.

[rickyyx]

ray/python/ray/_private/test_utils.py

Lines 1847 to 1865 in ce7764b

	def get_current_unused_port():
	"""
	Returns a port number that is not currently in use.
	This is useful for testing when we need to bind to a port but don't
	care which one.
	Returns:
	A port number that is not currently in use. (Note that this port
	might become used by the time you try to bind to it.)
	"""
	sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
	# Bind the socket to a local address with a random port number
	sock.bind(("localhost", 0))
	port = sock.getsockname()[1]
	sock.close()
	return port

FYI