Fix onBasePowerPriority support for moves

[TylerPohn]

Restore onBasePowerPriority: 4 to the 9 moves that use onBasePower handlers for base power modification. These values were removed in 628f32e as part of a TypeScript cleanup, but they were functional - the event system in battle.ts correctly reads and uses these priorities via resolvePriority().

Also adds onBasePowerPriority to the MoveEventMethods interface, following the existing pattern of onDamagePriority.

Fixes #5443

[Slayer95]

I don't believe this is correct. Please add tests that confirm that your change is effective if you are sure.

[urkerab]

What I can confirm is that runEvent with onEffect = true does run the effect's handler at the specified priority; we use this to ensure that False Swipe triggers Endure but not Sturdy.

[Slayer95]

What I can confirm is that runEvent with onEffect = true does run the effect's handler at the specified priority; we use this to ensure that False Swipe triggers Endure but not Sturdy.

I see you fixed priority for onEffect in #7879 (two years after the original issue). It would have been nice to have your change be more explicitly documented for visibility, but it's nice to see this issue finally fixed.

[Slayer95]

It's possible the relevant priority values have drifted in the meantime, so a researcher would still have to confirm this, imo.