Log sending and receiving every message in the transaction two phase commit protocol

The log lines will be added at log level 0 while sharded transactions are being tested and stabilized, but the lines can either be removed or their log level reduced afterwards.

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Update: The log lines were added at log level 3, but the default level for the kTransaction log component when running a test through resmoke.py was set to 4 for both local testing and evergreen.