Add more tests for REINDEX DATABASE/SYSTEM with relfilenode changes

Add more tests for REINDEX DATABASE/SYSTEM with relfilenode changes

Adding such commands in the main regression test suite is not a good
approach performance-wise as it impacts all the objects in the
regression database, so this additional coverage is added in the TAP
tests of reindexdb where we already run a few REINDEX commands with
SYSTEM and DATABASE so there is no runtime difference for the test.
This additional coverage checks which relations are rewritten with
relfilenode changes, as of:
- a toast index in user table.
- a toast index in catalog table.
- a catalog index.
- a user index.

This test suite is something I have implemented for a separate patch
that reworks a bit the way we handle these two REINDEX behaviors, but it
has enough value in itself to be in a separate commit.  This also makes
easier to follow what actually changes once the REINDEX logic is
reworked (currently, DABATASE rewrites both catalog and user tables, and
SYSTEM works only on catalogs).

Discussion: https://postgr.es/m/YtOqA7ldcJQADEE8@paquier.xyz