[mlir] Tighten the rules around folding TensorLoadOp
tensor_load(tensor_to_memref(x)) -> x is an incorrect folding because it ignores potential aliasing.
This revision approximates no-aliasing by restricting the folding to occur only when tensor_to_memref
is immediately preceded by tensor_load in the same block. This is a conservative step back towards
correctness until better alias analysis becomes available.
Differential Revision: https://reviews.llvm.org/D97957