[shell] clean up toDisposeOnActiveChanged properly

[akosyakov]

What it does

• fix the explorer view collapses spontaneously #7891: clean up toDisposeOnActiveChanged properly

How to test

• test that focus transfered from closed editor to another for different layouts
• rename a file via the navigator context menu while an editor is opened, check that the navigator does not get closed, but an editor is renamed

Review checklist

• as an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• as a reviewer, I agree to behave in accordance with the review guidelines

[akosyakov]

cc @corneliusludmann

[spoenemann]

👍

[vince-fugnitto]

The changes look fine to me, I was however unable to reproduce the issue on master
(I tried multiple times).

[jankeromnes]

It indeed seems to be a bit hard to reproduce. I tried renaming files about 20 times, and only saw the bug 2 or 3 times. (Seems to be easier when it's the right-most editor, and/or when you select the file in the navigator before renaming, not quite sure.)

[akosyakov]

I can reproduce it quite reliably:

• focus editor
• then trigger rename of this file from the navigator via the context menu