Revert "Add ability for `ModalRoutes` to ignore pointers during transitions and do so on `Cupertino` routes (#95757)" (#104520)

This reverts commit 4c0b0be2.

Add ability for `ModalRoutes` to ignore pointers during transitions and do so on `Cupertino` routes (#95757)

This reverts commit c82ddd39.

This reverts commit 5fd259be.

This reverts commit 43e31977

* Reland "Android Q transition by default (#82670)"

This reverts commit 4053b4b1.

* Fix `overall_experience_test.dart` for flutter_tools

This reverts commit a1ae4fea.

This reverts commit d056500b.

This reverts commit 31de052e.

This reverts commit e2490f29.

Adds Navigator.maybeOf to replace calling Navigator.of(context, nullOk: true), and removes the nullOk parameter. Also changes Navigator.of to return a non-nullable value, and removes many (120!) instances of the ! operator, reducing the possible places where a null dereference could occur.

Updated references to the old button classes to the new ones in comments and documentation for tests in the material and cupertino libraries. (#62164)

* Add material page, cupertino page, and transition page classes

* update

* update comments

* fix test

* addressing comments

* make page getter private

* add language version 2.8 in packages/flutter

* enable non-nullable analyzer flag

Fix tests that rely on FadeTransition incorrectly and depend on implementation details of FadeUpwardsTransitionBuilder (#51150)