Fixes #1363

Please note that this doesn't prompt when you try to send a message with a bad command.

Since this causes crashes on some qml module updates.

Fixes #1383
Fixes #1132

fixes #1355

So far we haven't seen any reduction in issues about database
corruption, so presumably this is unrelated and the lag is annoying.

Instead of completing the list of Linux, Windows and the BSDs (NetBSD and
DragonFly would still be missing), simply flip it to not-macOS to simplify
and fix the two other aforementioned BSDs at once.

CMake builds ManagerLinux.cpp on `!MAC && !WIN`, that is BSD and Linux.
Fix the Linux-only assumption in the shared header.

Qt's `Q_OS_UNIX` is defined on Linux, BSDs and macOS alike.

See also:
https://daniel.haxx.se/blog/2023/01/08/copyright-without-years/
https://hynek.me/til/copyright-years/

fixes #1182

Especially the emoji array shrinks a lot with this, but adds a few extra
relocations on startup. But it removes a lot of exception handling code
at runtime, which is nice and possibly this is still faster.

Also fix rerendering edited messages after keys are received.

fixes #1375
fixes #770
fixes #888

fixes #1373

Also add them to the communities sidebar

Fixes #809

GStreamer 1.22 merged the videoscale plugin into the videoconvertscale
plugin. So we should check if the Element is still loadable instead of
checking the plugin name.

fixes #1352

fixes #1350