QuickInput: First Element Fallback on Enter

[FernandoAscencio]

What it does

Closes #11979

How to test

1. Run Theia
2. Open as a many quick input menus as you can think of
3. Check that the first item on each of them is highlighted unless there is an active setting such as Dark (Theia) theme.

Some example menus that have been tested:

1. ? or the help menu
2. > or the command menu
3. F5 on Attach By Process ID
4. Quick checkout menu in the status bar
5. New Terminal (With Profile)... menu
6. Ctrl+K, Ctrl+T or the Color Theme menu.
7. File Icon Theme menu.
8. This plugin.
9. Using the Internal QuickPick command added in this request.

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

Signed-Off-By: FernandoAscencio fernando.ascencio.cama@ericsson.com

[msujew]

Looks good to me 👍 I can confirm that the first element is always selected in case there's no explicit selection made programmatically.

[msujew]

@FernandoAscencio Before I merge this PR, do you mind rebasing your PR onto the latest master? Just to confirm that your changes aren't the reason that the Ubuntu build pipeline is failing.

[FernandoAscencio]

@FernandoAscencio Before I merge this PR, do you mind rebasing your PR onto the latest master? Just to confirm that your changes aren't the reason that the Ubuntu build pipeline is failing.

Should be done