[inductor] Move size asserts to C++, fix bug (#87028)
Inductor internally models any `size=1` dimension as having `stride=0` to simplify indexing formulas (sympy will remove these terms from the expression).
This caused a bug in our generate stride assert in detectron2_maskrcnn_r_50_fpn, where we asserted the wrong stride of a size==1 dimension.
This fixes that bug, and moves size/stride assert logic to C++ which should be a small perf gain.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/87028
Approved by: https://github.com/anijain2305
