When we have both const and non-const version of a function, we import
the non-cont version with the "Mutating" suffix. This logic, however, is
redundant for static member functions as those can never be marked as
"const" since they don't have a "self" or "this" to mutate.
rdar://120858502
Fixes https://github.com/apple/swift/issues/66326
This allows us to reneable Windows method tests. Note that Windows still has
a broken convention for non-trivial record with non-trivial destructor but
trivial copy-constructor, so classes in the methods.swift test need an explicit
copy constructor.
Fixes rdar://88391102
