Add git blame error reporting with notification (#10408)

<img width="1035" alt="Screenshot 2024-04-11 at 13 13 44"
src="https://github.com/zed-industries/zed/assets/13402668/cd0e96a0-41c6-4757-8840-97d15a75c511">

Release Notes:

- Added a notification to show possible `git blame` errors if it fails to run.

Caveats:
- ~git blame now executes in foreground
executor  (required since the Fut is !Send)~

TODOs:
- After a failed toggle, the app thinks the blame
is shown. This means toggling again will do nothing
instead of retrying. (Caused by editor.show_git_blame
being set to true before the git blame is generated)
- ~(Maybe) Trim error?~ Done

---------

Co-authored-by: Thorsten Ball <mrnugget@gmail.com>

crates/git/src/blame.rs

@@ -78,6 +78,7 @@ fn run_git_blame(
         .arg(path.as_os_str())
         .stdin(Stdio::piped())
         .stdout(Stdio::piped())
+        .stderr(Stdio::piped())
         .spawn()
         .map_err(|e| anyhow!("Failed to start git blame process: {}", e))?;