Enforce that custom nodes and resources created via the "Create New Node" dialog, should permanently retain their original type (script). This means:
- Type continuity: It should be impossible for the user to (accidentally) clear the original script of a custom node that was created via the "Create New Node" dialog.
- Extensibility: The user should be able to extend custom types as usual (create a script that inherits the original type and replace the original script of that node with his own). However, if he then clears his extension-script from that node later on, the custom type should revert to its original script instead of becoming a non-scripted type.
We need to update the scene root in multiple singletons to ensure that
certain flags are correct. This is what `EditorNode::set_edited_scene()`
does.
Usually we use `replace_by` to complete the replacement of the scene
root. Call `EditorNode::set_edited_scene()` when the `replacing_by`
signal is emitted to set the new scene root. This is suitable when
using a single node to replace, which may be problematic if the
replacing node is a tree. Because during the call to `replace_by()`,
the new node and its child nodes will enter tree during `parent->
add_child(p_node)`, and later emits the `replacing_by` signal.
When the parent scene has to be reloaded because the child scene
changes and switches to the parent scene, there is no need to use
`replace_by()` since the scene's diffs are already saved.
This change introduces a new EditorThemeManager class
to abstract theme generatio and its subroutines.
Logic related to EditorTheme, EditorColorMap, and editor
icons has been extracted into their respective files with
includes cleaned up.
All related files have been moved to a separate folder to
better scope them in the project. This includes relevant
generated files as well.
Resource path should not be attempted to be taken over, as that's not intended for copy-paste and fails anyway, but this results in the whole paste operation failing as well
This should result in some noticeable performance improvements,
aside from fixing bugs due to conflicts in logic.
This also simplifies some related code identified while debugging.
