[mob][photos] Create a top level generic filter to be used for search ResultTypes(s) for which we don't plan to keep a subtype of HierarchicalSearchFilter

mobile/lib/models/search/hierarchical/hierarchical_search_filter.dart

@@ -10,7 +10,9 @@ abstract class HierarchicalSearchFilter {
   //adding/removing applied filters. An exception where results can be all files
   //in gallery is when the filter is the initial filter (top level) of the
   //gallery.
-  final Set<int> matchedUploadedIDs = {};
+  final Set<int> matchedUploadedIDs;
+
+  HierarchicalSearchFilter({this.matchedUploadedIDs = const <int>{}});
 
   String name();
   IconData? icon();

mobile/lib/models/search/hierarchical/top_level_generic_filter.dart

@@ -0,0 +1,59 @@
+import "package:flutter/material.dart";
+import "package:flutter/widgets.dart";
+import "package:photos/models/file/file.dart";
+import "package:photos/models/search/hierarchical/hierarchical_search_filter.dart";
+
+///Not necessary that all top level filters in hierarchical search have to be
+///a [TopLevelGenericFilter].
+class TopLevelGenericFilter extends HierarchicalSearchFilter {
+  final String filterName;
+  final int occurrence;
+  final IconData? filterIcon;
+
+  TopLevelGenericFilter({
+    required this.filterName,
+    required this.occurrence,
+    required super.matchedUploadedIDs,
+    this.filterIcon,
+  });
+
+  @override
+  bool isMatch(EnteFile file) {
+    throw UnimplementedError(
+      "isMatch is not ment to be called by design for TopLevelGenericFilter. "
+      "isMatch is used for checking if files match the filter and then to add "
+      "the file's uploaded fileIDs to the filter's matchingFileIDs list. For "
+      "top level filters, matchingFileIDs should be set when the filter is "
+      "initialised since the results are passed to the widget where it's "
+      "initialised.",
+    );
+  }
+
+  @override
+  Set<int> getMatchedUploadedIDs() {
+    return matchedUploadedIDs;
+  }
+
+  @override
+  bool isSameFilter(HierarchicalSearchFilter other) {
+    if (other is TopLevelGenericFilter) {
+      return other.filterName == filterName;
+    }
+    return false;
+  }
+
+  @override
+  String name() {
+    return filterName;
+  }
+
+  @override
+  IconData? icon() {
+    return filterIcon;
+  }
+
+  @override
+  int relevance() {
+    return occurrence;
+  }
+}