Add constraint options to SearchAnchor suggestions builder (#148856)

Refactors the `SearchAnchor` suggestions builder to not take up the whole screen

https://github.com/flutter/flutter/issues/148852

dev/tools/gen_defaults/lib/search_view_template.dart

@@ -50,6 +50,9 @@ class _${blockName}DefaultsM3 extends ${blockName}ThemeData {
   @override
   EdgeInsetsGeometry? get barPadding => const EdgeInsets.symmetric(horizontal: 8.0);
 
+  @override
+  bool get shrinkWrap => false;
+
   @override
   Color? get dividerColor => ${componentColor('md.comp.search-view.divider')};
 }