Use the standard initdb mechanism for it, instead of having bespoken code
in gpinitsystem.

Also remove the unnecessarily complicated logic to generate gp_toolkit.sql
from gp_toolkit.sql.in. All the JETPACK_* variables were constants, and
there is particular need in making the gp_toolkit functions relocatable to
different schemas or prefixes, so just hardcode them and remove the sed
magic.

Rewrite the file header of gp_toolkit.sql. The legal blurp is not needed,
make the header look more like that of information_schema.sql and
system_views.sql.

Remove compaction_info.sql. It was only needed for old in-place
upgrade from 4.3.x to 4.3.4.2, which is not relevant for master branch.

Fix the "jetpack" bugbuster regression test. It was originally written to
test the gp_toolkit views, but gp_toolkit was in fact not installed in
bugbuster, and the expected output just contained a bunch of "relation
does not exist" errors. Now it actually tests gp_toolkit again. Some of
the test queries didn't produce repeateable results, due to differing oids,
differences in table sizes, and other tables created by previous tests, so
fixed those too.

This has a small user-visible difference: gp_toolkit schema is now also
installed in template0. That caused the difference in the expected outputs:
pg_regress creates the "regression" database using template0 as the
template, so gp_toolkit used to not be installed in it, but it is now.