Rename targeted jstests for transaction two phase commit to txn_two_phase_commit_*.js

The following tests should get renamed:

jstests/sharding/txn_basic_two_phase_commit.js
jstests/sharding/txn_coordinator_commands_basic_requirements.js
jstests/sharding/txn_failover_two_phase_commit.js
jstests/sharding/txn_commit_coordination_is_robust_to_killop.js
jstests/sharding/transactions_recover_decision_from_local_participant.js
jstests/sharding/txn_wait_for_majority_commit_after_stepup.js