Consider more ways to obfuscate scalar constants

Currently spirv-fuzz only obfuscates scalar constants by replacing them with known uniform values. But it could do various other things, e.g. a constant 10 could be replaced by (x - 30) if x is known to hold the value 40.

Some more adventurous things should be tried in due course.

No file or test is identified in the issue. Start by locating spirv-fuzz’s existing scalar-constant obfuscation, then define and agree on specific additional transformations such as replacing 10 with (x - 30) when x is known to be 40; done means the selected transformations are implemented and tested.

Written by the indexing model from the issue text.