ui/ux: fix bug induced by PR #12604

[vladarama]

What it does

This PR fixes a bug that was induced in #12604 where the styling for input fields would not be displayed properly. An example would be the input field appearing when renaming a file. This was caused by overflow: hidden being applied on all text-inputs. Now, the overflow: hidden will only be applied to the vsx-extension-search-bar which requires it.

Before:

After:

How to test

1. Start Theia, open the Extensions or the Source Control views
2. Resize the view, making it smaller
3. The input field should be responsive, with the text overflow hidden by an ellipsis
4. Try renaming a file, the input field should be styled correctly

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

[vince-fugnitto]

I can confirm the bug on master, and that this change successfully fixes it 👍