Errorprone: Change error setup

Add ErrorProneChecksWarning. Do not use "-XepAllErrorsAsWarnings." This
improves the pickup of new warnings in newer versions, and shows what
further options could be enabled.

Bug: 72971960
Test: m RUN_ERROR_PRONE=true javac-check
Change-Id: Ia4416d941e65ad0b9ba5e23dadf3c304c8df5f10