This reverts #9053 and #9375 because they introduced a regression on
`main` that broke the titlebars on macOS:
Two things are off:
- Left padding is missing
- Titlebar height is less than it was before, which means the
traffic-light buttons are not centered vertically
What @as-cii and I noticed while looking into this: the `cfg!(macos)`
macros that were used don't work like that. You need to check for
`cfg!(target = "macos")` etc. Means that on macOS we never used the
macOS-specific code because the condition was always false.
Overall height, we're not sure about.
Release Notes:
- N/A
