[material_ui] DrawerButton and NavigationRail omit Semantics states #194904

In packages/material_ui, assistive technologies across platforms (TalkBack, VoiceOver, NVDA, JAWS) are not informed of drawer expand/collapse state on DrawerButton and EndDrawerButton or tab selection roles on NavigationRail destinations (WCAG 4.1.2 Name, Role, Value):

1. DrawerButtonIcon & EndDrawerButtonIcon missing expanded semantics (b/460308840, b/461982793): action_buttons.dart#L288-L367 builds the drawer action icon without setting Semantics.expanded from ScaffoldState.isDrawerOpen / isEndDrawerOpen, omitting SemanticsFlag.isExpanded on /drawer and /navigation-drawer.
2. NavigationRail destinations missing tabBar / tab roles: navigation_rail.dart#L520-L553 and navigation_rail.dart#L961-L985 omit SemanticsRole.tabBar on the destination group and SemanticsRole.tab on _RailDestination (unlike TabBar and Tab in tabs.dart), exposing destinations as generic buttons instead of tabs and duplicating the "Tab i of n" indexLabel on web where SemanticsRole.tabBar (role="tablist") already exposes set size.

Proposed Fix

• Set Semantics(expanded: ...) on DrawerButtonIcon and EndDrawerButtonIcon when an ancestor Scaffold has a drawer or endDrawer (flutter/packages#13176).
• Assign SemanticsRole.tabBar to NavigationRail's destination group and SemanticsRole.tab (with MergeSemantics and non-web indexLabel, matching TabBar/Tab) to _RailDestination (flutter/packages#13176).

# DrawerButton / EndDrawerButton before fix:
SemanticsData(flags: [isButton, isEnabled, isFocusable], label: "Open navigation menu")
# Missing: isExpanded (true when drawer is open, false when closed)

# NavigationRail & _RailDestination before fix:
SemanticsData(role: SemanticsRole.none, flags: [isSelected, isButton, isFocusable], label: "First\nTab 1 of 3")
# Expected: parent SemanticsRole.tabBar + child SemanticsRole.tab