[MU4 Issue] Multi-instances: different versions of the MuseScore should not communicate

[cbjeukendrup]

Describe the bug In principle, stable and pre-release versions of MuseScore should be able to be installed independently, and never influence each other in any way.

But with the multi-instances system, all versions of MuseScore 4 will communicate with each other, share settings and other stuff, and mess things up, even though they still use distinct folders for app/user data.

To Reproduce Steps to reproduce the behavior:

1. Have a stable and an unstable version of MuseScore 4 installed. (For example, the alpha 2 build was marked as stable (erroneously?).)
2. Have both running at the same time.
3. Change settings in one, and see that these settings are propagated to the other one. That should not happen.

Expected behavior So, stable/unstable versions should only communicate with other instances of the same kind as themselves.

We might also want to take the version number into account, i.e. version 4.0.1 cannot communicate with 4.0.0. Or even just the path to the executable, to make sure that only instances of the exact same build can communicate. The could prevent "miscommunications" between versions, that might occur when we change how instances communicate exactly. I'm not sure whether we would want to do this though.

Platform information

• OS: reported on macOS