Remove non-existing global class from cache

[miv391]

Fixes problems with deleting script files containing global classes.

• When a script file containg a global class is externally deleted, Godot editor doesn't handle this gracefully. Editor keeps spamming errors, but doesn't fix the situation.
• When a directory is removed in Godot editor, directory's files are more or less ignored and global classes from those files are not properly removed. Master assumes wrongly that EditorFileSystem's scan will handle the situation, but it doesn't.

Fixes #81867

Test cases

Test project contains two new classes, my_good_sprite_2d.gd located in root and another in bad/my_bad_sprite_2d.gd.

g42_cache_test.zip

1. Open Godot and test project

2. Start adding new node by clicking + button in Scene tree.
   --> SUCCESS: MyBadSprite2D is possible node type, no errors

3. Delete directory "bad"

4. Start adding new node by clicking + button in Scene tree.
   --> FAIL: You get errors

1. Close Godot and delete my_good_sprite_2d.gd from file system
2. Open Godot and test project
3. Start adding new node by clicking + button in Scene tree.
   --> FAIL: Now you errors also from MyGoodSprite2D

The only situation where removing classes from cache file works, is when only files, not directories, are deleted in Godot editor.

Fixes

The reason for the errors is that the global classes made by the user are not properly removed from .godot/global_script_class_cache.cfg.

• Changes in create_dialog.cpp fix the situation when files are deleted externally. When a non-existing global class is detected, it is removed from the cache. This prevents further errors.

• Changes in dependency_editor.cpp fix the situation when a folder containing a class file is deleted in Godot editor. When directories are deleted, master doesn't process each deleted file the same way as single deleted files are processed. Instead it is assumed that EditorFileSystem's scan will handle this, but it doesn't. Scan doesn't notice deleted directories at all. Now for every deleted file, EditorFileSystem's update_file is called and the global class (if file contains one) is deleted from cache file.

[KoBeWi]

Not sure if CreateDialog should be responsible for cleaning classes..

[KoBeWi]

This is wrong. It makes every file deleted separately when deleting directories.
You should still use files_to_delete for this action.

[KoBeWi]

Is this always necessary? When you delete directory, this should be handled by rescan (like in the old code).

[miv391]

Then maybe the rescan should be fixed? Currently it doesn't handle delete directories. There is some code to handle deleted directories, but it is never called (at least not when directories are deleted from FileSystem).

[KoBeWi]

Well I was more asking whether this line fixes anything. If there is a case not handled by the above lines then this one could stay.

[akien-mga]

Superseded by #90186. Thanks for the contribution!