Add --add/--new to control CLI behaviour (#9202)

When neither is specified, if you open a directory you get a new
workspace, otherwise files are added to your existing workspace.

With --new files are always opened in a new workspace
With --add directories are always added to an existing workspace

Fixes #9076
Fixes #4861
Fixes #5370

Release Notes:

- Added `-n/--new` and `-a/--add` to the zed CLI. When neither is
specified, if you open a directory you get a new workspace, otherwise
files are added to your existing workspace. With `--new` files are
always opened in a new workspace, with `--add` directories are always
added to an existing workspace.
([#9076](https://github.com/zed-industries/zed/issues/9096),
[#4861](https://github.com/zed-industries/zed/issues/4861),
[#5370](https://github.com/zed-industries/zed/issues/5370)).

crates/recent_projects/src/recent_projects.rs

@@ -493,9 +493,16 @@ mod tests {
                 }),
             )
             .await;
-        cx.update(|cx| open_paths(&[PathBuf::from("/dir/main.ts")], app_state, None, cx))
-            .await
-            .unwrap();
+        cx.update(|cx| {
+            open_paths(
+                &[PathBuf::from("/dir/main.ts")],
+                app_state,
+                workspace::OpenOptions::default(),
+                cx,
+            )
+        })
+        .await
+        .unwrap();
         assert_eq!(cx.update(|cx| cx.windows().len()), 1);
 
         let workspace = cx.update(|cx| cx.windows()[0].downcast::<Workspace>().unwrap());