Replace ProjectEntry struct with ProjectEntryId

Previously, we tracked the worktree_id and entry_id separately, but now that entry ids are unique across all worktrees this is unnecessary.

Co-Authored-By: Max Brunsfeld <maxbrunsfeld@gmail.com>
Co-Authored-By: Keith Simmons <keith@the-simmons.net>

crates/diagnostics/src/diagnostics.rs

@@ -449,7 +449,7 @@ impl workspace::ItemView for ProjectDiagnosticsEditor {
         None
     }
 
-    fn project_entry(&self, _: &AppContext) -> Option<project::ProjectEntry> {
+    fn project_entry_id(&self, _: &AppContext) -> Option<project::ProjectEntryId> {
         None
     }