[SROA] Improve handleling of assumes bundles by SROA

This patch fixes this crash https://gcc.godbolt.org/z/Ps8d1e
And gives SROA the ability to remove assumes if it allows promoting an alloca to register
Without removing assumes when it can't promote to register.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D86570