### Godot version

4.0b17

### System information

macOS 13.2

### Issue description

The shader function fma, used by the visual shader UVFunc node generated code:
```
// UVFunc:5
vec2 n_in5p1 = vec2(6.00000, 6.00000);
vec2 n_in5p2 = vec2(0.50000, 0.50000);
vec2 n_out5p0 = fma((UV - n_in5p2), n_in5p1, n_in5p2);
```
Does not seem to be defined in the Compatibility renderer, causing shader compilation to fail if it's used with a lot of errors and debug output (10000+ messages as it prints out a lot of engine shader code?). Ending with the relevant errors:
 ```
drivers/gles3/shader_gles3.cpp:242 - SceneShaderGLES3: Fragment shader compilation failed:
  ERROR: 0:928: Invalid call of undeclared identifier 'fma'
  ERROR: 0:930: Use of undeclared identifier 'm_n_out5p0'
  
  drivers/gles3/shader_gles3.cpp:342 - Method/function failed.
```

Simple shader using fma in Mobile:
![Screenshot 2023-02-08 at 09 52 38](https://user-images.githubusercontent.com/17763524/217483066-fe0feab7-72c4-4db7-a44e-041a1ad93f25.jpg)

Switch to Compatibility renderer:
![Screenshot 2023-02-08 at 09 53 27](https://user-images.githubusercontent.com/17763524/217483149-4fdef308-67cf-40d2-8d4a-d72dc7c85e70.jpg)



### Steps to reproduce

- Start a project in Mobile
- Make a shader where you use the fma function, for example the shader below in the reproduction field. Or a visual shader using the UVFunc node.
- Assign the shader to a shader material and apply this to a visible mesh, observe it renders
- Switch project to Compatibility renderer
- See errors and failed shader compilation

### Minimal reproduction project

Minimal test shader, use in Compatibility renderer:

```
shader_type spatial;

void fragment() {
	vec2 n_in5p1 = vec2(6.00000, 6.00000);
	vec2 n_in5p2 = vec2(0.50000, 0.50000);
	vec2 n_out5p0 = fma((UV - n_in5p2), n_in5p1, n_in5p2);

	ALBEDO = vec3(1,0,0);
}

```
used_functions[p_identifier].used = true;
			}
			break;
		case IdentifierType::IDENTIFIER_LOCAL_VAR:
			if (HAS_WARNING(ShaderWarning::UNUSED_LOCAL_VARIABLE_FLAG) && used_local_vars.has(p_function) && used_local_vars[p_function].has(p_identifier)) {
				used_local_vars[p_function][p_identifier].used = true;
			}
			break;
		default:
			break;
	}
}
#endif 
bool ShaderLanguage::_find_identifier(const BlockNode *p_block, bool p_allow_reassign, const FunctionInfo &p_function_info, const StringName &p_identifier, DataType *r_data_type, IdentifierType *r_type, bool *r_is_const, int *r_array_size, StringName *r_struct_name, ConstantNode::Value *r_constant_value) {
	if (is_shader_inc) {
		for (int i = 0; i < RenderingServer::SHADER_MAX; i++) {
			for (const KeyValue<StringName, FunctionInfo> &E : ShaderTypes::get_singleton()->get_functions(RenderingServer::ShaderMode(i))) {
				if ((current_function == E.key || E.key == "global" || E.key == "constants") && E.value.built_ins.has(p_identifier)) {
					if (r_data_type) {
						*r_data_type = E.value.built_ins[p_identifier].type;
					}
					if (r_is_const) {
						*r_is_const = E.value.built_ins[p_identifier].constant;
					}
					if (r_type) {
						*r_type = IDENTIFIER_BUILTIN_VAR;
					}
					return true;
				}
			}