Correctly model undefined behavior in {tensor|memref}.dim

These operations have undefined behavior if the index is not less than the rank of the source tensor / memref, so they cannot be freely speculated like they were before this patch.  After this patch we speculate them only if we can prove that they don't have UB.

Depends on D135505.

Reviewed By: mravishankar

Differential Revision: https://reviews.llvm.org/D135748