Create an Instance Pass framework

[rdaly525]

Create an Instance Pass framework

[rdaly525]

The way that LLVM does this is they have all the 'Uses' of a function within a LLVM::Module, and you have a command that just says replace all instances with this other instance.

I could do the same thing for CoreIR where I basically keep pointers to all instances (within a namespace) which use a specific Module. Then add a function from module that says replace all instnaces of this module with other module.

[rdaly525]

Should have a function like:

Instantiable* replaceAllUsesWith(Instantiable*)

[rdaly525]

This was already put in