Align writing of generated Slang shaders with GLSL

[tdavidovicNV]

This brings GenSlang tests to be in line with GenGlsl, and disables the writing of tested shaders to disk.

The main motivation is that the tests (both Slang and GLSL) actually currently produce invalid code for the NG_lightcompoundtest node, which is confusing.

[kwokcb]

Can we add (to Slang) update (GLSL) addSkipNodeDefs() tester override to include ND_lightcompoundtest ?

[tdavidovicNV]

Can we add (to Slang) update (GLSL) addSkipNodeDefs() tester override to include ND_lightcompoundtest ?

I am sorry, I am not exactly sure what you mean by those two parentheses.
I've added it to the GenSlang addSkipNodeDefs(). Should I add it to GenGlsl as well?

[jstone-lucasfilm]

@tdavidovicNV @kwokcb Let's keep this change focused on Slang, and we can address the GLSL exception in a separate PR. Based on recent discussions on the MaterialX Slack, I'm getting the sense that we'll ultimately want to remove the light compound node entirely, as it's no longer used by any of the teams in our community, so that may end up being the next step for that specific exception in Slang and GLSL render tests.

[jstone-lucasfilm]

Thanks for the fix, @tdavidovicNV!