Support "functors" for code reflection utilities (#58891)
As a follow-up to https://github.com/JuliaLang/julia/pull/57911, this
updates:
- `Base.method_instance`
- `Base.method_instances`
- `Base.code_ircode`
- `Base.code_lowered`
- `InteractiveUtils.code_llvm`
- `InteractiveUtils.code_native`
- `InteractiveUtils.code_warntype`
to support "functor" invocations.
e.g. `code_llvm((Foo, Int, Int))` which corresponds to `(::Foo)(::Int,
::Int)`
