Wrong background for color dialog

[Jacalz]

Checklist

• I have searched the issue tracker for open issues that relate to the same problem, before opening a new one.
• This issue only relates to a single bug. I will open new issues for any other problems.

Describe the bug

The advanced color dialog picker wheel has a dark rectangular background because it still uses the old background color and not theme.OverlayBackgroundColor() outside of the circle.

How to reproduce

1. Open the dialogs panel in fyne_demo.
2. Open the advanced color picker and open up the advanced accordion.
3. Notice the black rectangle around the color wheel.

Screenshots

Example code

See fyne_demo.

Fyne version

8b4fd1e

Go compiler version

Go 1.20.7

Operating system and version

Fedora Linux 38

Additional Information

I opened #4198 but there is some weird behaviour of the test images. In general, the all of the code for the color dialog probably needs a make over. The code has not really been touched in years since the original developer left the project. The code is complicated and doesn't follow our code standards of today. It is just silently rotting away...