Implement Feature Build Profiles

This PR is a continuation of #50381 (which was implemented exactly a year ago!)

* Add a visual interface to select which classes should not be built into Godot (well, they are built if something else uses them, but if not used the optimizer will remove them out).
* Add a detection system to scan the project and figure out the actual classes used.
* Added the ability for SCons to load build profiles.

Obligatory Screen:

A simple test with a couple of nodes in the scene resulted in a 25% reduction for the final binary size

TODO:

* Script languages need to implement used class detection (left for another PR).
* Options to disable servers or server functionalities (like 2D or 3D physics, navigation, etc). Are missing, that should also greatly aid in reducing binary size.
* Options to disable some modules would be desired.
* More options to disable drivers (OpenGL, Vulkan, etc) would be desired.

In general this PR is a starting point for more contributors to improve and enhance this functionality.

3 files changed, 18 insertions, 7 deletions

diff --git a/core/object/class_db.cpp b/core/object/class_db.cpp
index ac008dad88..d67315f20d 100644
--- a/core/object/class_db.cpp
+++ b/core/object/class_db.cpp
@@ -305,6 +305,13 @@ void ClassDB::add_compatibility_class(const StringName &p_class, const StringNam
 	compat_classes[p_class] = p_fallback;
 }
 
+StringName ClassDB::get_compatibility_class(const StringName &p_class) {
+	if (compat_classes.has(p_class)) {
+		return compat_classes[p_class];
+	}
+	return StringName();
+}
+
 Object *ClassDB::instantiate(const StringName &p_class) {
 	ClassInfo *ti;
 	{
diff --git a/core/object/class_db.h b/core/object/class_db.h
index 1d26eb18f1..8b6a260d86 100644
--- a/core/object/class_db.h
+++ b/core/object/class_db.h
@@ -357,6 +357,7 @@ public:
 	static bool is_resource_extension(const StringName &p_extension);
 
 	static void add_compatibility_class(const StringName &p_class, const StringName &p_fallback);
+	static StringName get_compatibility_class(const StringName &p_class);
 
 	static void set_current_api(APIType p_api);
 	static APIType get_current_api();
@@ -418,16 +419,16 @@ _FORCE_INLINE_ Vector<Error> errarray(P... p_args) {
 
 #endif
 
-#define GDREGISTER_CLASS(m_class)                    \
-	if (!GD_IS_DEFINED(ClassDB_Disable_##m_class)) { \
-		::ClassDB::register_class<m_class>();        \
+#define GDREGISTER_CLASS(m_class)             \
+	if (m_class::_class_is_enabled) {         \
+		::ClassDB::register_class<m_class>(); \
 	}
-#define GDREGISTER_VIRTUAL_CLASS(m_class)            \
-	if (!GD_IS_DEFINED(ClassDB_Disable_##m_class)) { \
-		::ClassDB::register_class<m_class>(true);    \
+#define GDREGISTER_VIRTUAL_CLASS(m_class)         \
+	if (m_class::_class_is_enabled) {             \
+		::ClassDB::register_class<m_class>(true); \
 	}
 #define GDREGISTER_ABSTRACT_CLASS(m_class)             \
-	if (!GD_IS_DEFINED(ClassDB_Disable_##m_class)) {   \
+	if (m_class::_class_is_enabled) {                  \
 		::ClassDB::register_abstract_class<m_class>(); \
 	}
 
diff --git a/core/object/object.h b/core/object/object.h
index 705d6451dc..17f75a4e1d 100644
--- a/core/object/object.h
+++ b/core/object/object.h
@@ -358,6 +358,7 @@ private:
 	friend class ::ClassDB;                                                                                                                      \
                                                                                                                                                  \
 public:                                                                                                                                          \
+	static constexpr bool _class_is_enabled = !bool(GD_IS_DEFINED(ClassDB_Disable_##m_class)) && m_inherits::_class_is_enabled;                  \
 	virtual String get_class() const override {                                                                                                  \
 		if (_get_extension()) {                                                                                                                  \
 			return _get_extension()->class_name.operator String();                                                                               \
@@ -667,6 +668,8 @@ public: // Should be protected, but bug in clang++.
 	_FORCE_INLINE_ static void register_custom_data_to_otdb() {}
 
 public:
+	static constexpr bool _class_is_enabled = true;
+
 	void notify_property_list_changed();
 
 	static void *get_class_ptr_static() {