Introduce sidebar bookmarks page

fix https://github.com/brave/brave-browser/issues/20500

Applied bookmark part of chromium's side panel to sidebar bookmark panel.
sidebar.mojom is used for interacting between sidebar's bookmarks panel
with SidebarBookmarksPageHandler.
Most of webui impls in browser/resources/sidebar/bookmarks are copied from upstream
and modified to show bookmark part only.
(side panel's page shows read later and bookmark part both.)
Bookmarks page uses custom context menu by asking to native via
Sidebar:ShowCustomContextMenu interface.

chromium_src/python_modules/tools/json_schema_compiler/feature_compiler_helper.py

@@ -0,0 +1,20 @@
+# Copyright (c) 2022 The Brave Authors. All rights reserved.
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this file,
+# You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# When update this method, feature_compiler.py should be touched to make
+# feature_compiler.py run. json_feature target doesn't have this in its
+# dependency.
+# below discard list comes from common/extensions/api/_api_features.json.
+def DiscardBraveOverridesFromDupes(dupes):
+    dupes.discard('topSites')
+    dupes.discard('extension.inIncognitoContext')
+    dupes.discard('bookmarkManagerPrivate')
+    dupes.discard('bookmarks')
+    dupes.discard('settingsPrivate')
+    dupes.discard('sockets')
+    dupes.discard('sockets.tcp')
+    dupes.discard('sockets.udp')
+    dupes.discard('sockets.tcpServer')
+    dupes.discard('tabs')