Upstream postgres will probably soon push some changes that will change the
semantics of explain_get_index_name_hook_type. The returned index name will
automatically be properly quoted if needed, while it was previously the
extension's duty to take care of that, which hypopg failed to do. See
discussion at https://postgr.es/m/flat/16502-57bd1c9f913ed1d1%40postgresql.org
for more details.
To avoid build failure when the change is committed, change brin regression
test to match an hypothetical index name whether is quoted or not, similarly to
how it's done in all other regression tests.
Hypothetical BRIN indexes are broken in some minor versions of pg10, pg11 and
pg12. Detect those versions and warn users with a useful error message
recommending to update their minor versions of postgres.
Also add regression tests to make sure that support BRIN hypothetical indexes
doesn't get broken again.
