Address new proposed leaderboard filter behavior

[hburn7]

Objective

The way leaderboard filters work currently is very strange. @AkinariHex proposed in Discord that we change the behavior to the following:

• Replace current leaderboard filter behavior with new behavior as defined below.
• By default, on the frontend, no items are checked. This is the default leaderboard.
• When a user engages the filtering system by clicking one of the checkboxes, any tier checked should be specifically included in the results. If the user clicks all checkboxes, or has no checkboxes checked, the leaderboard will return in its unfiltered state.

Acceptance Criteria

• Leaderboard filter no longer uses nullable bools (bool?) and instead uses the standard bool type.
• Tiers with the filter as true will be explicitly included in the query, assuming no other criteria prevents them from showing up (e.g. if someone searches for bronze players with 3000 rating, the query will not return any results).
• Tiers with the filter as false will not be included if any other tiers are listed as true. Otherwise, no logic is performed
• If all tiers are marked as true, return the default leaderboard.