pg_dump only selected components of ACCESS METHODs

dumpAccessMethod() didn't get the memo that we now have a bitfield for
the components which should be dumped instead of a simple boolean.

Correct that by checking if the relevant bit is set for each component
being dumped out (and not dumping it out if it isn't set).

This corrects an issue where CREATE ACCESS METHOD commands were being
included in non-binary-upgrades when an extension included an access
method (as the bloom extensions does).

Also add a regression test to make sure that we only dump out the
ACCESS METHOD commands, when they are part of an extension, when doing
a binary upgrade.

Pointed out by Thom Brown.