Refactor AwardsHandler into ES class syntax

Simply converts AwardsHandler into a proper es2015 class and replaces all AwardsHandler.prototype.xxx with method definitions.

Since this type of change (mostly in indentation) produces a messy diff on gitlab.com, I wanted to do this as a separate MR from the rest of my refactors leading up to #33391 (closed) so that the changes I make from here are easier to understand.

Apart from changing the class definition syntax, nothing else has changed. This should make it easy to review.