Merge pull request #11104 from drewda/patch-1

Adding additional plugins to debugging guide [ci skip]
`inspect` for AR model classes does not initiate a new connection.

Conflicts:
	activerecord/CHANGELOG.md
Fix rake test_sqlite3_mem

Clearly nobody uses this except me. It's fast people!
Fix test

Oops. We need to estalish/remove the connection in the setup/teardown,
else it messes with the fixtures.
Fix indentation