### 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)

return (p_type == TK_OP_ASSIGN ||
			p_type == TK_OP_ASSIGN_ADD ||
			p_type == TK_OP_ASSIGN_SUB ||
			p_type == TK_OP_ASSIGN_MUL ||
			p_type == TK_OP_ASSIGN_DIV ||
			p_type == TK_OP_ASSIGN_MOD ||
			p_type == TK_OP_ASSIGN_SHIFT_LEFT ||
			p_type == TK_OP_ASSIGN_SHIFT_RIGHT ||
			p_type == TK_OP_ASSIGN_BIT_AND ||
			p_type == TK_OP_ASSIGN_BIT_OR ||
			p_type == TK_OP_ASSIGN_BIT_XOR);
}
bool ShaderLanguage::is_token_hint(TokenType p_type) {
	return int(p_type) > int(TK_RENDER_MODE) && int(p_type) < int(TK_SHADER_TYPE);
}
bool ShaderLanguage::convert_constant(ConstantNode *p_constant, DataType p_to_type, ConstantNode::Value *p_value) {
	if (p_constant->datatype == p_to_type) {
		if (p_value) {
			for (int i = 0; i < p_constant->values.size(); i++) {
				p_value[i] = p_constant->values[i];
			}
		}
		return true;
	} else if (p_constant->datatype == TYPE_INT && p_to_type == TYPE_FLOAT) {
		if (p_value) {
			p_value->real = p_constant->values[0].sint;
		}