editor: Select first match in "Find all references" editor (#13424)

Previously we've placed cursor on the first line of the first excerpt in
the multibuffer, but alas,
https://x.com/fasterthanlime/status/1804883499809165473 happened (j/k,
this feedback is totally valid) and now we're gonna place it at the end
of the first reference. As a bonus, with the old configuration `editor:
select next` tripped over itself. Now it's possible (& feasible) to do a
"select next" in "find all references"; consecutive referenced ranges
will be selected.

Fixes #13419



Release Notes:

- Fixed a bug where "Find all references" editor had cursor placed on
the first line of the first excerpt in the multibuffer instead of having
it on the first reference.

crates/editor/src/editor.rs

@@ -9181,6 +9181,12 @@ impl Editor {
             Editor::for_multibuffer(excerpt_buffer, Some(workspace.project().clone()), true, cx)
         });
         editor.update(cx, |editor, cx| {
+            if let Some(first_range) = ranges_to_highlight.first() {
+                editor.change_selections(None, cx, |selections| {
+                    selections.clear_disjoint();
+                    selections.select_anchor_ranges(std::iter::once(first_range.clone()));
+                });
+            }
             editor.highlight_background::<Self>(
                 &ranges_to_highlight,
                 |theme| theme.editor_highlighted_line_background,