[mlir][sparse] Distinguishing "shape" from "sizes" in variable names

I'm using "shape" to mean the compile-time object, where zeros indicate sizes which are compile-time dynamic; and using "sizes" to mean the run-time object, where zeros indicate a dimension with no coordinates (hence resulting in trivial storage).  Because their semantics differ on zeros, it's important to keep them distinguished.  Although we do not define separate C++ types to capture the distinction, we can at least use variable names to do so.

This is (tangential) work towards fixing: https://github.com/llvm/llvm-project/issues/51652

Depends On D122057

Reviewed By: aartbik

Differential Revision: https://reviews.llvm.org/D122058