spirv-fuzz: Permute the order of types, variables and constants at module scope

The order in which types, variable and constants appear in a module could be permuted, as long as dependencies between instructions are preserved. For example, a variable declaration could not be swapped with the declaration of its type, but could be swapped with another variable declaration.

It would be worth looking at TransformationMoveBlockDown, and FuzzerPassPermuteBlocks, as inspiration for how to implement this; they work at the level of blocks in the module but the concept should be similar.

Start by reading TransformationMoveBlockDown and FuzzerPassPermuteBlocks for how SPIR-V transformations and block permutations preserve dependencies. Identify the module-scope types, variables, and constants covered by the transformation, then verify that their order can be permuted without moving an instruction before anything it depends on.

Written by the indexing model from the issue text.