Rename finfer, disassemble, and methods(function,types)

Redo of #3792 using @JeffBezanson 's names.

    finfer -> code_typed
    methods(function, types) -> code_lowered
    disassemble(function, types, true) -> code_native
    disassemble(function, types, false) -> code_llvm

code_lowered is just an alias; the other three remove the method they're renaming.