Fixed contrast in project panel and scrollbar (#2512)

Redo of https://github.com/zed-industries/zed/pull/2504 

This makes the different git locations individually style-able

Release Notes:

- Improve git contrast (preview only)
1b5be04f76Mikayla Maki committed on 5/22/2023, 10:59:02 PM· committed by GitHubparentsfb2f17ee4454f1
7 files changedLine totals unavailable