Replace variable name bytecode transformer with mappings generation

[zml2008]

Currently we provide variable names with bytecode transformation. This is fairly inflexible though.

Eventually, I'd like to add a way to add "mappings contributors" that receive a MappingSet and can operate on it however they want, by adding/removing/renaming mappings however they want. This would also allow us to customize official names however we want (pending output remapping support)

[kashike]

This would also allow us to customize official names however we want (pending output remapping support)

big 👎

[Zidane]

@kashike

I don't see an issue with providing the support, it isn't VanillaGradle that would be exercising said support.

One use case of this would be to do parameter mapping.