(stable) Remove the "ONLY_FULL_GROUP_BY" SQL mode setup warning and change the setup key for "STRICT_ALL_TABLES"

Summary:
Ref T13404. Except for one known issue in Multimeter, Phabricator appears to function properly in this mode. It is broadly desirable that we run in this mode; it's good on its own, and enabled by default in at least some recent MySQL.

Additionally, "ONLY_FULL_GROUP_BY" and "STRICT_ALL_TABLES" shared a setup key, so ignoring one would ignore both. Change the key so that existing ignores on "ONLY_FULL_GROUP_BY" do not mask "STRICT_ALL_TABLES" warnings.

Test Plan: Grepped for ONLY_FULL_GROUP_BY.

Maniphest Tasks: T13404

Differential Revision: https://secure.phabricator.com/D20791