Currently scroll bars that are in regions that are set to "region overlap" (like Tool Bar and Side Bar using a transparent background) will fully hide when your mouse is not near them. This PR removes that feature so that they are treated like in other areas. This way you can always see that there are portions of the region scrolled away and what proportion. A less jarring transition since it is only 0.4 - 1.0, rather than 0.0 - 1.0. Pull Request: https://projects.blender.org/blender/blender/pulls/136571