edit predictions: Cache settings across renders (#24581)

We were reading edit prediction settings too often, causing frames to be
dropped. We'll now cache them and update them from
`update_visible_inline_completion`.

Release Notes:

- N/A

crates/assistant/src/inline_assistant.rs

@@ -1255,7 +1255,7 @@ impl InlineAssistant {
                     editor.scroll_manager.set_forbid_vertical_scroll(true);
                     editor.set_show_scrollbars(false, cx);
                     editor.set_read_only(true);
-                    editor.set_show_inline_completions(Some(false), window, cx);
+                    editor.set_show_edit_predictions(Some(false), window, cx);
                     editor.highlight_rows::<DeletedLines>(
                         Anchor::min()..Anchor::max(),
                         cx.theme().status().deleted_background,