Implement Anything Goes metagame
Anything Goes is the metagame with no bans and no clauses.
It is a Smogon Metagame, though, so it enforces both HP Percentage Mod and Endless Battle Clause.
Endless Battle Clause is deemed a tool to annoy players that leads to nowhere.
It also goes against the game philosophy and the game itself has a turn
limit, that's why it's added.

There is no 'Standard Anything Goes' because its bans are always going to
be Unreleased and Illegal Pokemon, as well as cartridge limitations.
Update the Mega Pokemon check
There is no need to store whether the team has a mega anymore.
With the general use of pokemon.canMegaEvo and it being set to false for
the whole team after a mega evolution, it is what we need to check to avoid
more than one mega evolution or banned mega evolutions.
Implement Mega Rayquaza Ban for Ubers
Mega Rayquaza is banned from Ubers.
However, Rayquaza with the move Dragon Ascent is allowed.
It is thus necessary to add a mod rule, Mega Rayquaza Ban Mod,
which flags Rayquaza as not mega evolveable.