Move git state to Project (#23208)

This restores its visibility outside of git_ui, which we'll need soon,
while preserving its per-project character.

Release Notes:

- N/A

crates/git_ui/Cargo.toml

@@ -17,7 +17,6 @@ anyhow.workspace = true
 collections.workspace = true
 db.workspace = true
 editor.workspace = true
-futures.workspace = true
 git.workspace = true
 gpui.workspace = true
 language.workspace = true
@@ -28,7 +27,6 @@ serde.workspace = true
 serde_derive.workspace = true
 serde_json.workspace = true
 settings.workspace = true
-sum_tree.workspace = true
 theme.workspace = true
 ui.workspace = true
 util.workspace = true