Replace chevron icon with codicon

[msujew]

What it does

Closes #9744

Replaces the chevron svg with a codicon.

How to test

1. Assert that the chevron still behaves as expected.
2. Switch to a light theme.
3. Observe that the chevron is colored 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]

The changes work well for me 👍
I confirmed that it works for multiple trees (explorer, file-dialog, siw, problems).