Provide more help around GRANT errors, particularly for missing TEMPORARY TABLE permission

Summary:
Fixes T13622. Figuring out what permissions we have seems difficult, so address this a bit more narrowly:

• Make the "access denied" error message a bit more helpful.
• Tailor error handling for the "CREATE TEMPORARY TABLE" statement.

Test Plan:

• Created a new user, granted them "SELECT ON *.*" but not "CREATE TEMPORARY TABLE", ran bin/storage upgrade --force --apply phabricator:20210215.changeset.02.phid-populate.php.
• Before: fairly opaque error.
• After: fairly useful error.

Subscribers: PHID-OPKG-gm6ozazyms6q6i22gyam

Maniphest Tasks: T13622

Differential Revision: https://secure.phabricator.com/D21608