DEV: raises a GrantError instead of a log and a variable exception (PR #12875)

The message in logs will now look like:

BadgeGranter::GrantError: Failed to backfill 'Some Badge' badge: {:post_ids=>[]}. Reason: ERROR:  column "email" does not exist
LINE 6: ...t id as user_id, current_timestamp as granted_at, email from...

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