Fix `Core.invoke` for `OpaqueClosure` (#61944)

This allows `cache_method` to work with builtins.

It would be preferable to remove the [`jl_opaque_closure_method` special
case](https://github.com/JuliaLang/julia/blob/2045dc97e05c3c241fb0c4b29c211e6a404ee399/src/gf.c#L152)
from `jl_specializations_get_linfo_`, but OpaqueClosures currently
overload the `(::OpaqueClosure)(....)` Method to store `invoke` adapters
so OpaqueClosure cannot de-specialize its MethodInstances like most
built-ins.

I plan to clean that up next, but for now this is sufficient to fix this
bug.