fire onDidChangeActiveEmitter when quick-pick is accepted

[vinokurig]

What it does

Set selected quick-pick item as active when a quick-pick item is chosen. This fixes a bug when the active items list is not actual on quick-pick accept event.

fixes eclipse-che/che#19030

How to test

1. Compile and start the sample plugin or download the sample plugin binary to the plugins folder.
2. Run F1 => Test Quick-pick and chose Second or Third item.
3. See: chosen item is printed in a notification.

In the current master theia only First item is returned.

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

[RomanNikitenko]

@vinokurig

I can not reproduce the issue for the master branch using your test-plugin - it works well for me without any changes.

[RomanNikitenko]

I see that here you use quickPick.selectedItems[0]. Should it be activeItems instead?

[vinokurig]

Yes, you are right, I am sorry I forgot to update the sample plugin. Now the plugin has been updated.

[RomanNikitenko]

Tested using provided test-plugin - it works well for me!

[vinokurig]

@RomanNikitenko thank you for the review!

[RomanNikitenko]

@vinokurig
please remove the branch if it's not used anymore

thanks!