style: Debug Variable styling fix

[FernandoAscencio]

What it does

Fixes: #12085 via CSS

The commit fixes the styling of the debug variables tree-view section including:

• respecting spaces between the variable and the value
• displaying ellipsis when content takes too much space

How to test

Reproduce the steps on #12085

1. start the application with theia as a workspace
2. set a breakpoint in a *.spec.ts file
3. start a debug session with run mocha tests config
4. confirm the styling of the debug variables is correct (spacing and ellipsis)
5. add a watch variable
6. confirm the styling to dismiss the variable is correct

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

[vince-fugnitto]

LGTM 👍

I confirmed that:

• debug variables respect spacing
• the handling of overflow of debug variables is correctly rendered and displays ellipsis
• the "dismiss" functionality of "watch expressions" is correctly rendered