[FunctionAttrs] Consider recursive argmem effects (PR63936)

When inspecting the function body, we can't simply ignore effects
of functions in the SCC entirely, because an argmem access of a
recursive call might result in an access to another location in
the callee.

Fix this by separately tracking memory effects that would occur if
the SCC accesses argmem, and then later add those.

Fixes https://github.com/llvm/llvm-project/issues/63936.

Differential Revision: https://reviews.llvm.org/D155956