Cleanup: Shuffle Squid result codes (aka log tags) into class LogTags

Cleanup: Shuffle Squid result codes (aka log tags) into class LogTags

This begins the migration of result codes from enumeration to a
set of flags whih can combine into much more flexible logging of
transation activity than hard-coded labels enumerating every
individual code path.

The existing ABORTED and TIMEDOUT state flags are also moved into
the new class as an example of how such flags would operate.