action_sheet: Choose "Close" and "Cancel" consistently for bottom sheets

This fixes the two inconsistencies flagged in discussion:
  https://chat.zulip.org/#narrow/channel/530-mobile-design/topic/bottom.20sheet.20.22Cancel.22.2F.22Close.22.20button/near/2216116

> I think it's reasonable to have both labels, but I think we should
> choose them differently than now:
>
> - "Cancel" when the sheet is about doing an action: [etc.]
>
> - "Close" when the sheet just presents information or nav options:
>   [etc.]

Author: chrisbobbe

lib/widgets/action_sheet.dart

@@ -92,7 +92,7 @@ void _showActionSheet(
                           child: SingleChildScrollView(
                             padding: const EdgeInsets.symmetric(vertical: 8),
                             child: MenuButtonsShape(buttons: optionButtons)))),
-                        const ActionSheetCancelButton(),
+                        const BottomSheetDismissButton(style: BottomSheetDismissButtonStyle.cancel),
                       ]))),
               ]))));
     });
@@ -160,12 +160,22 @@ abstract class ActionSheetMenuItemButton extends StatelessWidget {
   }
 }
 
-class ActionSheetCancelButton extends StatelessWidget {
-  const ActionSheetCancelButton({super.key});
+/// A stretched gray "Cancel" / "Close" button for the bottom of a bottom sheet.
+class BottomSheetDismissButton extends StatelessWidget {
+  const BottomSheetDismissButton({super.key, required this.style});
+
+  final BottomSheetDismissButtonStyle style;
 
   @override
   Widget build(BuildContext context) {
     final designVariables = DesignVariables.of(context);
+    final zulipLocalizations = ZulipLocalizations.of(context);
+
+    final label = switch (style) {
+      BottomSheetDismissButtonStyle.cancel => zulipLocalizations.dialogCancel,
+      BottomSheetDismissButtonStyle.close => zulipLocalizations.dialogClose,
+    };
+
     return TextButton(
       style: TextButton.styleFrom(
         minimumSize: const Size.fromHeight(44),
@@ -180,12 +190,20 @@ class ActionSheetCancelButton extends StatelessWidget {
       onPressed: () {
         Navigator.pop(context);
       },
-      child: Text(ZulipLocalizations.of(context).dialogCancel,
+      child: Text(label,
         style: const TextStyle(fontSize: 20, height: 24 / 20)
           .merge(weightVariableTextStyle(context, wght: 600))));
   }
 }
 
+enum BottomSheetDismissButtonStyle {
+  /// The "Cancel" label, for action sheets.
+  cancel,
+
+  /// The "Close" label, for bottom sheets that are read-only or for navigation.
+  close,
+}
+
 /// Show a sheet of actions you can take on a channel.
 ///
 /// Needs a [PageRoot] ancestor.

lib/widgets/emoji_reaction.dart

@@ -518,7 +518,7 @@ class _EmojiPickerState extends State<EmojiPicker> with PerAccountStoreAwareStat
               states.contains(WidgetState.pressed)
                 ? designVariables.contextMenuItemBg.withFadedAlpha(0.20)
                 : Colors.transparent)),
-            child: Text(zulipLocalizations.dialogClose,
+            child: Text(zulipLocalizations.dialogCancel,
               style: const TextStyle(fontSize: 20, height: 30 / 20))),
         ])),
       Expanded(child: InsetShadowBox(

lib/widgets/home.dart

@@ -324,7 +324,8 @@ void _showMainMenu(BuildContext context, {
                 child: AnimatedScaleOnTap(
                   scaleEnd: 0.95,
                   duration: Duration(milliseconds: 100),
-                  child: ActionSheetCancelButton())),
+                  child: BottomSheetDismissButton(
+                    style: BottomSheetDismissButtonStyle.close))),
             ])));
     });
 }

test/widgets/home_test.dart

@@ -231,7 +231,7 @@ void main () {
       await tapOpenMenuAndAwait(tester);
       checkIconSelected(tester, inboxMenuIconFinder);
       checkIconNotSelected(tester, channelsMenuIconFinder);
-      await tapButtonAndAwaitTransition(tester, find.text('Cancel'));
+      await tapButtonAndAwaitTransition(tester, find.text('Close'));
 
       await tester.tap(find.byIcon(ZulipIcons.hash_italic));
       await tester.pump();
@@ -265,10 +265,10 @@ void main () {
       await tapButtonAndAwaitTransition(tester, channelsMenuIconFinder);
     });
 
-    testWidgets('cancel button dismisses the menu', (tester) async {
+    testWidgets('close button dismisses the menu', (tester) async {
       await prepare(tester);
       await tapOpenMenuAndAwait(tester);
-      await tapButtonAndAwaitTransition(tester, find.text('Cancel'));
+      await tapButtonAndAwaitTransition(tester, find.text('Close'));
     });
 
     testWidgets('menu buttons dismiss the menu', (tester) async {