Use git config --global user.email for email address in automatic Co-authored-by (#32624)

Release Notes:

- Automatic population of `Co-authored-by` now uses `git config --global
user.email`

---------

Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>
Co-authored-by: Conrad <conrad@zed.dev>

crates/collab/src/db/tables/project_collaborator.rs

@@ -13,6 +13,8 @@ pub struct Model {
     pub user_id: UserId,
     pub replica_id: ReplicaId,
     pub is_host: bool,
+    pub committer_name: Option<String>,
+    pub committer_email: Option<String>,
 }
 
 impl Model {