Do not create multiple lambda callbacks for transaction commit.

After merging DBZ-137, the TransactionBuffer#registerCommitCallback accepts a lambda function that is essentially identical outside its arguments. It stands to reason this could be reworked such that the list of callbacks are instead metadata records that can be passed to a single function. See https://github.com/debezium/debezium-incubator/pull/185#discussion_r478461046.