google-vertexai[minor]: Move tests from gauth/webauth into vertexai packages #4506

Job	Run time
test-langchain-with-latest-deps	4m 0s
test-anthropic-with-latest-deps	3m 25s
test-anthropic-with-lowest-deps	3m 26s
test-community-with-latest-deps	4m 36s
test-community-with-lowest-deps	4m 37s
test-langchain-with-lowest-deps	4m 11s
test-openai-with-latest-deps	3m 9s
test-openai-with-lowest-deps	3m 24s
	30m 48s

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