debugger: First slight pass at UI (#27034)

- Collapse Launch and Attach into a single split button
- Fix code actions indicator being colored red.

Release Notes:

- N/A

crates/git_ui/Cargo.toml

@@ -49,7 +49,6 @@ serde.workspace = true
 serde_derive.workspace = true
 serde_json.workspace = true
 settings.workspace = true
-smallvec.workspace = true
 strum.workspace = true
 telemetry.workspace = true
 theme.workspace = true