Multiple fixes to affine loop tiling return status and checks

Fix crash in the presence of yield values. Multiple fixes to affine loop
tiling pre-condition checks and return status. Do not signal pass
failure on a failure to tile since the IR is still valid. Detect index
set computation failure in checkIfHyperrectangular and return failure.
Replace assertions with proper status return. Move checks to an
appropriate place earlier in the utility before mutation happens.

Differential Revision: https://reviews.llvm.org/D116738