spirv-fuzz: Transformation that adds synonyms by multiplying vectors and matrices by the identity matrix

Multiplying vectors and matrices by the identity matrix is an invariant operation. That is, we get the operand itself as a result.

The issue describes a spirv-fuzz transformation that multiplies vectors and matrices by the identity matrix to create equivalent results, but it names no files, tests, or entry points. First locate the existing spirv-fuzz transformation implementations and tests, then define the transformation's supported operands and verify that generated modules remain valid and semantically equivalent.

Written by the indexing model from the issue text.