Reverts "Normalize TabBarTheme (flutter#155476)" (flutter#155698)

Reverts: flutter#155476
Initiated by: eyebrowsoffire
Reason for reverting: The newly added tests are failing in postsubmit. See https://ci.chromium.org/ui/p/flutter/builders/prod/Windows%20framework_tests_libraries/19062/overview
Original PR Author: QuncCccccc

Reviewed By: {TahaTesser}

This change reverts the following previous change:
This PR is to make preparations to make `TabBarTheme` conform to Flutter's conventions for component themes:

* Added a `TabBarThemeData` class which defines overrides for the defaults for `TabBar` properties.
* Added 2 `TabBarTheme` constructor parameters: `TabBarThemeData? data` and `Widget? child`. This is now the preferred way to configure a `TabBarTheme`:
```
TabBarTheme(
  data: TabBarThemeData(labelColor: xxx, indicatorColor: xxx, ...),
  child: TabBar(...)
)
```
  These two properties are made nullable to not break existing apps which has customized `ThemeData.tabBarTheme`.

* Changed the type of component theme defaults from `TabBarTheme` to `TabBarThemeData`.

TODO:

* Fix internal failures.
* Change the type of `ThemeData.tabBarTheme` from `TabBarTheme` to `TabBarThemeData`. This may cause breaking changes, a migration guide will be created.

Addresses the "theme normalization" sub project within flutter#91772

dev/tools/gen_defaults/lib/tabs_template.dart

@@ -12,7 +12,7 @@ class TabsTemplate extends TokenTemplate {
 
   @override
   String generate() => '''
-class _${blockName}PrimaryDefaultsM3 extends TabBarThemeData {
+class _${blockName}PrimaryDefaultsM3 extends TabBarTheme {
   _${blockName}PrimaryDefaultsM3(this.context, this.isScrollable)
     : super(indicatorSize: TabBarIndicatorSize.label);
 
@@ -91,7 +91,7 @@ class _${blockName}PrimaryDefaultsM3 extends TabBarThemeData {
   static const EdgeInsetsGeometry iconMargin = EdgeInsets.only(bottom: 2);
 }
 
-class _${blockName}SecondaryDefaultsM3 extends TabBarThemeData {
+class _${blockName}SecondaryDefaultsM3 extends TabBarTheme {
   _${blockName}SecondaryDefaultsM3(this.context, this.isScrollable)
     : super(indicatorSize: TabBarIndicatorSize.tab);