[test] improve style for abc-version-message.py and rename to abc_p2p_version_timestamp.py

Summary:

• Rename the test to be more descriptive, and use an allowed name prefix
• Respect line length (88 chars)
• use blocktools.TIME_GENESIS_BLOCK instead of magic number
• add some documentation
• replace comments with test logging
• check the peer id in the debug log

This change is in preparation for a behavior change and additional test in D13357/

Test Plan: ninja check-functional

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D13369