GLES3: Ensure all ShaderData is properly initialized in set_code

[akien-mga]

• Fixes Warning spam in Compatibility renderer: Attempting to use a shader that requires tangents with a mesh that doesn't contain tangents.  #84418 (at least it should, didn't test yet as this needs an optimized build).
• Supersedes Ensure members are initialized in compatibility renderer SceneShaderData #84599.

I refactored the code to be clearer and hopefully prevent such errors in the future, but it's still quite error prone. The config booleans could maybe be moved to an internal struct that would always be zero'ed in set_code, so this can all be done in a single line instead of listing them all one by one.

I noticed that version doesn't get reset when calling set_code; I suppose this is intended.

Some ShaderData implementations initialized most of their booleans before the early return with empty code, while others did them after declaring gen_code. I unified to be like the former which seems to be the least bug prone (doesn't assume that none of these will be accessed when valid = false), but I could refactor the other way around if preferred.

[akien-mga]

I can't reliably trigger the warning locally with GCC builds, so would be good if @jsjtxietian or @chrisl8 could confirm that it fixes the issue for them.

[chrisl8]

Will test later today.

[chrisl8]

@akien-mga Yes, this appears to fix the issue entirely:

v4.2.beta.custom_build [e38686f] (master at the moment)

v4.2.beta.custom_build [0e04203]

[YuriSizov]

I can see that they are probably unused, but are you sure?

[akien-mga]

It wouldn't compile after the removal if they were used anywhere.

[YuriSizov]

Superficially it looks okay, but I would wait for the rendering team to confirm. The composition and order in the header may matter, and can't judge if your changes there are safe.

[jsjtxietian]

Yes, this appears to fix the issue entirely:

Same for me.

[clayjohn]

Looks great to me! In theory it doesn't matter if we initialize before or after the early return as we set valid to false (so the shader should be ignored anyway). But I think its safer to initialize before to ensure everything is default and we aren't accidentally relying on old state.