[pre-RFC] Name mangling in IRModules

[areusch]

@Mousius

A Pass which looks for variables with matching name_hints within a module and updates it to remove collisions with any other names in the module. With the additional rule that a global_symbol which strictly enforce the name, un-resolvable collisions would be an error.

Is the idea here to use pointer equality to determine when two Var with the same name reference the same logical thing? not sure how we differentiate between uses across the IRModule otherwise.