Refactor tier update reports

[scheibo]

stats/stats/src/reports.ts

Line 373 in 50b3c1b

async tierUpdateReport(

provides an example that at one point implemented tier update reports correctly for the singles metagame at the time. It needs to be updated to match the reports produced by https://github.com/smogon/usage-stats/blob/main/TierUpdate9Singles.py, though likely can also be simplified somewhat (see for example #5)

Furthermore, we need the following reports to be added:

• https://github.com/smogon/usage-stats/blob/main/TierUpdate9Doubles.py
• https://github.com/smogon/usage-stats/blob/main/TierUpdate9LC.py
• https://github.com/smogon/usage-stats/blob/main/TierUpdate9NatDex.py

Finally, all of these reports need to be tested, so this is blocked on #3

[scheibo]

This is a good first issue because it is:

a) simply porting logic
b) very contained and doesn't involve much knowledge of anything else within this repository, its mostly just a question of implementing one (complicated) function
c) it is very easy to test - unlike logs/stats processing which relies on (private) logs data, the usage reports rely on data which is fully public

[scheibo]

July seems like a good month to update the reports tesdts to https://www.smogon.com/forums/threads/usage-based-tier-update-for-july-2024-august-38-september-52.3746220/

[scheibo]

OK these are technically all implemented, though the implementation feels like it could use some cleaning up. Going to repurpose the issue to be a sanity check + refactoring