The metadata_track suite was originally part of cdbfast, dating back
around 10-11 years. It was later moved into bugbuster around six years
ago, already then with doubts as to what it actually did. After the
open sourcing we scrapped bugbuster, moving anything worthwhile (or
just not analyzed for usefulness yet) into the normal regress schedule
which is where metadata_track remained till now. This all according to
memory and the old proprietary issue tracker.

Looking at metadata_track, it's entirely duplicative only issuing
lots of DDL already tested elsewhere without verifying the results,
most likely since it was originally testing the metadata tracking
of the operations. Since the latter part is no longer happening,
move parts of the test into the existing pg_stat_last_operation
test and remove the rest, as the remaining value of this quite slow
test (spending ~10-12 minutes serially in the pipeline) is highly
debatable.

The existing pg_stat_last_operation was, and I quote, "underwhelming"
so most of it is replaced herein. There is still work to be done in
order to boost metadata tracking test coverage, but this is at least
a start.

Reviewed-by: Jimmy Yih