Handle Slide In Unmanaged Notification in the non-selected repo

[mkondratek]

1. As for now, only the snapshot of the repository selected in Git Machete panel is available (not all snapshots of all repositories!).
2. The unmanaged branch notification works on the same snapshot as the one selected in Git Machete panel.

Hence, we must assure that the current branch changed belongs to the same repository as the given snapshot.

A handling of all repositories (not only selected) is a subject to of improvement.

Originally posted by @mkondratek in #1531 (comment)

[PawelLipski]

This might have serious performance/memory footprint implications tho in case of projects with multiple VCS roots... to be considered

[PawelLipski]

A handling of all repositories

Also, there's a question if that's really what the users are willing to see... multiple notifications popping up at once, for multiple VCS roots (some of which they might not be interested in managing under Git Machete at all) 🤔

[mkondratek]

multiple notifications popping up at once

nothing like this for sure! Let's recall the (single line Xd) scenario here:

1. Checkout an unmanaged branch from a repository that is not currently selected in Git Machete tab.
   (this can be done via DVCS widget or command line)

So as one can perform only a single checkout at once there would be only a single notification at that time.