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.
* Automatically selects the newly created directory
* Automatically selects "res://" when nothing is selected
* Fixes an error when overwrite/replace dialog appears
* Changes "copy checkbox + action button" to "copy button + move button"
* Double clicking a directory (un)collapses it instead of copy/move
* Uses DirectoryCreateDialog for "Create Folder"
