This is required to add support for Stadium in unit tests. A lot of the
codebase assumes that all mods start with "gen" followed by a number,
but I don't want to touch the others at the moment.
It was in Mirror Coat rather than Counter.
Also switch to checking for "activated", so it doesn't conflict
with #7702 (committed separately so git blame still shows me as
test author)
It turns out not creating a format on-the-fly breaks deserialization.
We now just use the same custom-rule system that tournaments use.
Some hacks are currently necessary (many tests assume that we're
playing in Anything Goes rather than Custom Game) but we'll work them
out in time.
In most other similar systems, like TeamValidator, we use `thing.dex` instead of having it extend `ModdedDex`. Battle has always extended `ModdedDex`, though. This changes Battle to match the others.
This should fix an issue with `Battle.data` not being cached.
This also frees up Battle to extend ObjectReadWriteStream<string> in a future update.
