We want to retain *some* of the full paths in order to test more code paths.
But the default should be to use the command name only. This makes the tests
less visually cluttered.
Rename TEST-23-TYPE-EXEC to TEST-23-UNIT-FILE and merge it with
following tests:
- TEST-37-RUNTIMEDIRECTORYPRESERV
- TEST-40-EXEC-COMMAND-EX
- TEST-41-ONESHOT-RESTART
- TEST-42-EXECSTOPPOST
- TEST-57-ONSUCCESS-UPHOLD