[Bug]: Adding margin to widgets or padding to the panel breaks centering between spacers

[luisbocanegra]

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Describe the bug
Adding margin to widgets or padding to the panel makes the spacers to misbehave, when widgets like Global menu appear and disappear the centered widget moves around breaking the whole purpose of the centering which is having the widget at a fixed position unless the content to the left/right goes past the center (e.g long global menus)

To Reproduce
Steps to reproduce the behavior:

1. Have one or more widgets centered between default Panel Spacer or Panel Spacer Extended widgets
2. Have one or more widgets that appear and disappear dynamically e.g Global Menu, Window buttons, Window Title and the like
3. Go to Appearance > Panel > Enable and set custom Padding values
4. Make the dynamic widgets hide and re-appear
5. Centered widget moves around

Expected behavior
Centered widgets should stay centered when there is not enough content to de-center them

Screenshots

Screencast_20241022_123755.mp4

Project version
1.0.0

Desktop (please complete the following information):

Operating System: Arch Linux
KDE Plasma Version: 6.2.1
KDE Frameworks Version: 6.7.0
Qt Version: 6.8.0
Kernel Version: 6.11.4-arch1-1 (64-bit)
Graphics Platform: Wayland
Processors: 12 × Intel® Core™ i7-9750H CPU @ 2.60GHz
Memory: 31.2 GiB of RAM
Graphics Processor: Mesa Intel® UHD Graphics 630

Additional context
Since Panel Colorizer applies modifications to the Plasma panel it's possible that a fix won't be accepted upstream, but will be available on Panel Spacer Extended widget