Make add_local_worktree private and use find_or_create_local_worktree

The former always adds a worktree, even if we have one already in the
project and that could be misused. The public API should always search
for a local worktree containing the requested path first so that the
project can uphold invariants about which worktrees it has.

crates/file_finder/src/file_finder.rs

@@ -457,7 +457,7 @@ mod tests {
         params
             .project
             .update(&mut cx, |project, cx| {
-                project.find_or_create_worktree_for_abs_path(Path::new("/root"), false, cx)
+                project.find_or_create_local_worktree("/root", false, cx)
             })
             .await
             .unwrap();
@@ -518,7 +518,7 @@ mod tests {
         params
             .project
             .update(&mut cx, |project, cx| {
-                project.find_or_create_worktree_for_abs_path(Path::new("/dir"), false, cx)
+                project.find_or_create_local_worktree("/dir", false, cx)
             })
             .await
             .unwrap();
@@ -584,11 +584,7 @@ mod tests {
         params
             .project
             .update(&mut cx, |project, cx| {
-                project.find_or_create_worktree_for_abs_path(
-                    Path::new("/root/the-parent-dir/the-file"),
-                    false,
-                    cx,
-                )
+                project.find_or_create_local_worktree("/root/the-parent-dir/the-file", false, cx)
             })
             .await
             .unwrap();