Make HarvestRegistry available from API and fix Mystical Agriculture crops with harvest ritual

[stellanera98]

• Added getHarvestRegistry() to IBloodMagicAPI and BloodMagicAPI
• Modified HarvestRegistry to not be static to make it consistent with other API things
• Moved the registration calls from ritual/ModRituals to impl/BloodMagicCorePlugin
• Removed compat with mods not in 1.20 and Pams HarvestCraft as I couldnt find a 1.20 version of the repo/api
• Added compat/MysticalAgricultureCompat, when its loaded it registers their crops. Uses the actual mag api jar instead of Class.forName() and such
• Added repository/dependencies for Mystical Agriculture (commented out the runtime stuff)
• Added version variables for mag and the needed cucumber library in gradle.properties

(Changed my setup again, auto-formatting doesnt seem to work all the time, hope i caught at least most of it)