Fixed Forecast and Flower Gift

[AgustinGDLV]

Description

This PR does the following:

• The now unused u8 TryWeatherFormChange has been removed (last remnant of old Castform hacks?).
• Flower Gift now correctly boosts its own and an ally's attack and special defense by 1.5x.
• Forecast and Flower Gift form changes work consistently with weather changes.
• Gastro Acid, Core Enforcer, Simple Beam, and Worry Seed revert Castform and Cherrim to normal in Gen 5+ (config added).
• Adds tests for Forecast and Flower Gift.

Tests Added

Issue(s) that this PR fixes

Fixes #2972.

Discord contact info

Agustin#1522

[AgustinGDLV]

Ready for review! I added a missing interaction with Air Lock (that also makes it pretty much impossible to test Strong Winds), reworked how the weather form reversion is done, and added all the missing tests. Castform is now functional with snow, too!

[AsparagusEduardo]

B_WEATHER_FORMS already exists.

In retrospect, I didn't properly communicate that I wanted Castform and Cherrim's generational changes to be handled by the form change tables, which is why I proposed the optional ability parameter, in order to toggle between them by changing the data.

[AgustinGDLV]

Added assumptions, ready again. Ignore the force push, I forgot committed code review changes don't just magically make their way onto my local repo, but the change was made in the new commit anyways so I just force pushed.