[Attributor][FIX] Prevent alignment breakage wrt. must-tail calls

If we have a must-tail call the callee and caller need to have matching
ABIs. Part of that is alignment which we might modify when we deduce
alignment of arguments of either. Since we would need to keep them in
sync, which is not as simple, we simply avoid deducing alignment for
arguments of the must-tail caller or callee.

Reviewed By: rnk

Differential Revision: https://reviews.llvm.org/D76673