Finish getting multiple diagnostics sources building and running

crates/editor/src/hover_popover.rs

@@ -620,7 +620,7 @@ mod tests {
                 }],
                 &snapshot,
             );
-            buffer.update_diagnostics(set, cx);
+            buffer.update_diagnostics(0, set, cx);
         });
 
         // Hover pops diagnostic immediately

crates/editor/src/multi_buffer.rs

@@ -2800,7 +2800,7 @@ impl MultiBufferSnapshot {
     ) -> impl Iterator<Item = DiagnosticEntry<O>> + 'a
     where
         T: 'a + ToOffset,
-        O: 'a + text::FromAnchor,
+        O: 'a + text::FromAnchor + Ord,
     {
         self.as_singleton()
             .into_iter()