[IPSCCP] Drop argmemonly after replacing pointer argument.

This patch updates IPSCCP to drop argmemonly and
inaccessiblemem_or_argmemonly if it replaces a pointer argument.

Fixes PR46717.

Reviewers: efriedma, davide, nikic, jdoerfert

Reviewed By: efriedma, jdoerfert

Differential Revision: https://reviews.llvm.org/D84432