Removed MixinEntityLivingBase reflection hack

[3arthqu4ke]

Describe the pull Removes a reflection hack done in MixinEntityLivingBase to keep compatibility with older Mixin versions.

Describe how this pull is helpful The comment above the hack describes it as a bit silly and bad for performance which is fixed here.

Additional context The reason the hack was added is because Mixin did not have this line prior to 0.8. In Mixin 0.7 the check typeInfo.isLoadable() (which would check if AccessorEntityFireworkRocket is an Accessor) did not exist, causing Mixin to try to find the class in the hierachy of EntityLivingBase. This only happens when a Mixin method is merged into the targeted class, and only for the methods of that Mixin class, so putting the methods inside a helper class fixes the issue.

Let me know if this is wanted and if the helper class should be a kotlin class instead.