Shadows cannot be disabled in the material in the Compatibility renderer

[nauta-turbidus]

Godot version

Godot v4.2.beta (b733901)

System information

Godot v4.2.beta (b733901) - Solus 4.4 - X11 - GLES3 (Compatibility) - Mesa Intel(R) HD Graphics 3000 (SNB GT2) () - Intel(R) Core(TM) i5-2500K CPU @ 3.30GHz (4 Threads)

Issue description

The shadows_disabled render mode doesn't work at all with the Compatibility renderer, it simply isn't implemented.

Steps to reproduce

-add any two MeshInstances to a 3D scene
-add a light so that shadow falls on one of the meshes
-add a new shader material to the shadowed mesh and create a shader
-add render_mode shadows_disabled; to the shader
-shadows are still visible

Minimal reproduction project

N/A

[YuriSizov]

Probably an oversight from #77496 ? cc @clayjohn

Edit: SHADOWS_DISABLED is defined in the material storage, but not used in the scene shader as far as I can tell.