[Attributor][FIX] Replace AANoFPClass MBEC propagation (#91030)

The old use of must-be-executed-context (MBEC) did propagate
through calls even if that was not allowed. We now only propagate from
call site arguments. If there are calls/intrinsics that allows
propagation, we need to add them explicitly.

Fixes: https://github.com/llvm/llvm-project/issues/78507



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Co-authored-by: Matt Arsenault <arsenm2@gmail.com>