### Godot version

4.0.beta16

### System information

Windows 10 Pro x64, GLES3, RTX 3080 Ti (528.02)

### Issue description

In Compatibility/GLES3 back-end, shaders which use a uniform to get the normal roughness buffer cannot compile. For example, the shader:
```glsl
shader_type spatial;

uniform sampler2D normal_roughness_texture : hint_normal_roughness_texture;

void fragment() {
    vec4 sample = texture(normal_roughness_texture, UV);
}
```
results in an error in the output:
```
  drivers/gles3/shader_gles3.cpp:242 - SceneShaderGLES3: Fragment shader compilation failed:
  0(890) : error C1503: undefined variable "normal_roughness_buffer"
  
  drivers/gles3/shader_gles3.cpp:342 - Method/function failed.
```

If I switch over to the Mobile or Forward+ backends, there is no shader compilation error.

### Steps to reproduce

Open the attached reproduction in the 4.0.beta16 editor.

When the scene is opened, the error is produced automatically:
1. Open `scene.tscn`
2. Open Output to review error

When the scene is saved with any changes made to the shader, the same error is also produced:
1. Open `scene.tscn`
2. Open `example.gdshader` in the shader editor.
3. Make a compile-able change to the shader.
4. Save the scene
5. Open Output to review the error

### Minimal reproduction project

[NormalRoughnessTexture_GLES3_Error.zip](https://github.com/godotengine/godot/files/10534253/NormalRoughnessTexture_GLES3_Error.zip)

StringName struct_name;
				bool is_local = false;
				if (p_block && p_block->block_tag != SubClassTag::TAG_GLOBAL) {
					int idx = 0;
					bool found = false;
					while (builtin_func_defs[idx].name) {
						if (builtin_func_defs[idx].tag == p_block->block_tag && builtin_func_defs[idx].name == identifier) {
							found = true;
							break;
						}
						idx++;
					}
					if (!found) {
						_set_error(vformat(RTR("Unknown identifier in expression: '%s'."), String(identifier)));
						return nullptr;
					}
				} else {
					if (!_find_identifier(p_block, false, p_function_info, identifier, &data_type, &ident_type, &is_const, &array_size, &struct_name)) {
						if (identifier == "SCREEN_TEXTURE" || identifier == "DEPTH_TEXTURE" || identifier == "NORMAL_ROUGHNESS_TEXTURE") {
							String name = String(identifier);
							String name_lower = name.to_lower();
							_set_error(vformat(RTR("%s has been removed in favor of using hint_%s with a uniform.\nTo continue with minimal code changes add 'uniform sampler2D %s : hint_%s, filter_linear_mipmap;' near the top of your shader."), name, name_lower, name, name_lower));
							return nullptr;
						}
						_set_error(vformat(RTR("Unknown identifier in expression: '%s'."), String(identifier)));
						return nullptr;
					}
					if (ident_type == IDENTIFIER_VARYING) {
						TkPos prev_pos = _get_tkpos();
						Token next_token = _get_token();