spirv-fuzz: Adjust the limit on the maximum number of parameters

`TransformationAddParameters` randomly adds new parameters to the function. However, we must make sure that we don't exceed the universal limit on this quantity which is `255` as of today (section 2.17 is SPIR-V spec). We also wouldn't want to end up having all functions with the `255` parameters. Thus, we are using a custom limit - `128` in `FuzzerContext`. Consider whether there is a better alternative for this number.

Start by reading TransformationAddParameters and FuzzerContext to understand how the current limit of 128 is applied. Compare possible alternatives against the SPIR-V universal limit of 255 and the goal of avoiding uniformly large parameter counts; the work is done when a justified limit strategy is implemented and covered by relevant tests.

Written by the indexing model from the issue text.