[Lazarus] Phasing out support for the Carbon widgetset

[Bart]

Since Lazarus 2.2.0 the Cocoa widget set has replaced the Carbon
widgetset as default widgetset on MacOS.
Apple has officially removed Carbon from macOS since 2019.
The Lazarus team has decided to minimize the effort to support the
Carbon widget set, so we can focus on stabilizing more used
widgetsets.

We want to review all open bug reports for Carbon.
If the issue is also present when using the Cocoa widget set, the
issue will be marked as such.
If it is not present with Cocoa the issue will be resolved with
resolution "suspended".
Patches to fix such issues are still welcome, but new bug reports for
the Carbon widget set are only accepted, if they contain a patch to
fix it.

Help from the community with cleaning up the bug tracker is
appreciated. If you test a Carbon issue with Cocoa, please leave your
findings as a note in the bugtracker.

The Lazarus developers will try not to break the current Carbon widget
set, but will not actively develop new features for it.

-- 
Bart