Polish Multi-File Diff Editor

[hediet]

### Tasks
- [ ] https://github.com/microsoft/vscode/issues/199291
- [x] Better Support For Renames
- [x] Better Support For Deleted Files
- [x] Better Support For New Files
- [ ] https://github.com/microsoft/vscode/issues/199295
- [ ] https://github.com/microsoft/vscode/issues/199615
- [ ] https://github.com/microsoft/vscode/issues/200336
- [ ] https://github.com/microsoft/vscode/issues/202064

[hediet]

Closing, as most issues are addressed.