2092186 - Add an "Add to group" item to the new browser menu

Status: NEW

(Firefox for Android :: Menu, task)

Description

[Petru-Mugurel Lingurar [:petru]]

The legacy browser menu (MenuDialogFragment) had an "Add to group" item in its "More" submenu (MoreSettingsSubmenu).
It was shown when the pref_key_show_tab_groups_in_menu secret setting (Settings.showTabGroupsInMenu) was enabled, and opened the tab group flow for the selected tab through MenuAction.Navigate.OpenTabGroupFlow with TabGroupFlowEntryPoint.AddTabToGroup.

The customizable menu (MenuFragment) never got an equivalent item.
Bug 2090842 would remove the legacy menu along with its "Add to group" item and the browser_menu_add_to_tab_group string, so the secret setting now has no effect and the tab group flow cannot be reached from the menu.

Expected: the browser menu offers "Add to group" for the selected tab, opening TabGroupFlowFragment with TabGroupFlowEntryPoint.AddTabToGroup.

Implementation notes:

• Add a menu item provider for it, registered in MenuItemProvidersFactory and placed in BrowserMenuConfiguration. It can navigate with the existing action_global_tabGroupFlowFragment global action.
• Reuse the showTabGroupsInMenu gate. It defaults to off because enabling it pushed Print out of the visible menu area, which the Print UI tests rely on (see DefaultTabManagementFeatureHelper); check whether that still applies to the new menu layout.
• MenuAction.Navigate.OpenTabGroupFlow and its telemetry branch in MenuTelemetryMiddleware (recording TabGroupFlowEntryPoint.telemetryName) are still in place and can be reused.