Removed uses of AppBarTheme.color in packages/flutter (#74273)

packages/flutter/lib/src/material/app_bar.dart

@@ -729,7 +729,7 @@ class _AppBarState extends State<AppBar> {
 
     final Color backgroundColor = backwardsCompatibility
       ? widget.backgroundColor
-        ?? appBarTheme.color
+        ?? appBarTheme.backgroundColor
         ?? theme.primaryColor
       : widget.backgroundColor
         ?? appBarTheme.backgroundColor

packages/flutter/lib/src/material/search.dart

@@ -229,7 +229,7 @@ abstract class SearchDelegate<T> {
     return theme.copyWith(
       appBarTheme: AppBarTheme(
         brightness: colorScheme.brightness,
-        color: colorScheme.brightness == Brightness.dark ? Colors.grey[900] : Colors.white,
+        backgroundColor: colorScheme.brightness == Brightness.dark ? Colors.grey[900] : Colors.white,
         iconTheme: theme.primaryIconTheme.copyWith(color: Colors.grey),
         textTheme: theme.textTheme,
       ),

packages/flutter/test/material/snack_bar_test.dart

@@ -741,7 +741,7 @@ void main() {
       materialTapTargetSize: MaterialTapTargetSize.shrinkWrap,
       applyElevationOverlayColor: false,
       pageTransitionsTheme: pageTransitionTheme,
-      appBarTheme: const AppBarTheme(color: Colors.black),
+      appBarTheme: const AppBarTheme(backgroundColor: Colors.black),
       scrollbarTheme: const ScrollbarThemeData(radius: Radius.circular(10.0)),
       bottomAppBarTheme: const BottomAppBarTheme(color: Colors.black),
       colorScheme: const ColorScheme.light(),

packages/flutter/test/material/theme_data_test.dart

@@ -291,7 +291,7 @@ void main() {
       materialTapTargetSize: MaterialTapTargetSize.shrinkWrap,
       applyElevationOverlayColor: false,
       pageTransitionsTheme: pageTransitionTheme,
-      appBarTheme: const AppBarTheme(color: Colors.black),
+      appBarTheme: const AppBarTheme(backgroundColor: Colors.black),
       scrollbarTheme: const ScrollbarThemeData(radius: Radius.circular(10.0)),
       bottomAppBarTheme: const BottomAppBarTheme(color: Colors.black),
       colorScheme: const ColorScheme.light(),
@@ -384,7 +384,7 @@ void main() {
       materialTapTargetSize: MaterialTapTargetSize.padded,
       applyElevationOverlayColor: true,
       pageTransitionsTheme: const PageTransitionsTheme(),
-      appBarTheme: const AppBarTheme(color: Colors.white),
+      appBarTheme: const AppBarTheme(backgroundColor: Colors.white),
       scrollbarTheme: const ScrollbarThemeData(radius: Radius.circular(10.0)),
       bottomAppBarTheme: const BottomAppBarTheme(color: Colors.white),
       colorScheme: const ColorScheme.light(),