[v1][Bugfix] Add extra_keys to block_hash for prefix caching

[heheda12345]

This pr adds extra key to block hash, to generate different hash value for two blocks with the same token string but different extra_keys in their parent blocks. For example, it can generate different hash value for the second block of the following two requests:

request1 = make_request(
        request_id=0,
        prompt_token_ids=[_ for _ in range(6)],
        mm_positions=[{
            "offset": 0,
            "length": 3
        }, {
            "offset": 3,
            "length": 3
        }],
        mm_hashes=["hash1", "hash2"],
    )
    request2 = make_request(
        request_id=1,
        prompt_token_ids=[_ for _ in range(6)],
        mm_positions=[{
            "offset": 0,
            "length": 3
        }, {
            "offset": 3,
            "length": 3
        }],
        mm_hashes=["hash3", "hash2"],
    )

[github-actions]

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[comaniac]

LGTM. Thanks for catching this