pg_bsd_indent: Collect test diffs in test.diffs instead of tests.diff

Remove trailing zero words from Bitmapsets

Remove local optimizations of empty Bitmapsets into null pointers.

Require empty Bitmapsets to be represented as NULL.

Mop up some undue familiarity with the innards of Bitmapsets.

Remove bms_first_member().

Integrate pg_bsd_indent into our build/test infrastructure.

Sync pg_bsd_indent's copyright notices with Postgres practice.

Import pg_bsd_indent sources.

Simplify and speed up pg_dump's creation of parent-table links.

Fix pg_dump for hash partitioning on enum columns.