Fa/quick input box fix

[FernandoAscencio]

Not sure if this is the proper way to fix the issue, but for the moment it helps.

From my understanding the issue lies in the way each of the quick input menus are being called. Some like the commands menu call the Quick Input menu through the open('filter') as seen in the following examples:

1. packages\core\src\browser\common-frontend-contribution.ts
2. packages\core\src\browser\quick-input\quick-command-frontend-contribution.ts
3. packages\plugin-ext-vscode\src\browser\plugin-vscode-commands-contribution.ts

As far as could tell, this is the main reason the quick input menu 'focuses' on the first option after a small amount of time. Thus, on Enter the first option is selected.

Other files call the showQuickPick<>() directly and open the Quick Input menu that way. Bypassing the open() function somehow. One example, and probably the most important one is packages\git\src\browser\git-quick-open-service.ts. Specifically the checkout() function which is called when the menu in question is opened.

What it does

This commit intends to close this issue using existing architecture.

How to test

Test is highlighted in the issue linked.

1. Open Theia with git extension enabled.
2. Click the branch name on the status bar.
3. Press enter.

The first item should be highlighted.

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