Add `modify_bounciness` power type.

[MerchantPug]

This PR adds the apoli:modify_bounciness power type. This changes the multiplier at which the player's existing velocity is applied upon landing on something.

Fields

• modifier/modifiers (Optional) | These fields should be self explanatory.
• block_condition (Optional) | the block condition to test against the landing block to determine whether the player should bounce on a block.
• take_fall_damage Boolean (Optional) | Whether the player should take fall damage upon bouncing, defaults to false.
• stage (Optional) | Either "pre" or "post". Determines at which stage of the calculation the modifier(s) should apply.
  • Pre is before the entity's velocity has been applied to the block's bounciness value.
  • Post is after the entity's velocity has been applied to the pre value.

Additional Info

This power may be a nightmare for compatibility with bouncy modded blocks, this is because there is no shared bounciness field in the base block class, they instead opted for hardcoded bounciness. I have tried circumventing this by adding a BouncinessMultiplierRegistry, which stores multipliers for bounciness for specific classes to use when this power is active.

[MerchantPug]

I think that the BouncinessMultiplierRegistry should not be a hardcoded thing now looking back at this.

[MerchantPug]

I'll be rewriting the hardcoded bounciness registry into a new thing for all power classes that allow them to define global data through datapacks.