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/project/src/project_tests.rs

@@ -1,7 +1,7 @@
 use crate::{Event, *};
+use ::git::diff::assert_hunks;
 use fs::FakeFs;
 use futures::{future, StreamExt};
-use git::diff::assert_hunks;
 use gpui::{AppContext, SemanticVersion, UpdateGlobal};
 use http_client::Url;
 use language::{