Support role queue

[cheshire137]

Need this in by September 1 for comp season 18. See https://playoverwatch.com/en-us/news/23060961/introducing-role-queue.

• [x] Add concept of a role to heroes
• [x] Track role SRs separately
• [x] Allow specifying which role you played per game
• [x] When a role is chosen, disable the heroes not in that role in the match form
• [x] When a hero is chosen, select the appropriate role in the match form