[material_ui, cupertino_ui] Deprecate Material and Cupertino

The [material.dart](https://github.com/flutter/flutter/blob/master/packages/flutter/lib/material.dart) and [cupertino.dart](https://github.com/flutter/flutter/blob/master/packages/flutter/lib/cupertino.dart) libraries should be deprecated in order to communicate to users that they are no longer supported and that users should migrate to material_ui and cupertino_ui.

In addition to the main libraries, anything else related to them should be deprecated as well, such as:

* [find.byTooltip](https://github.com/flutter/flutter/blob/9a353b5ad5e00932819a1ff959f0dc1a65af8f73/packages/flutter_test/lib/src/finders.dart#L396) as mentioned in https://github.com/flutter/flutter/issues/191063.

Start with packages/flutter/lib/material.dart and packages/flutter/lib/cupertino.dart, then inspect packages/flutter_test/lib/src/finders.dart for find.byTooltip. Review issue 191063 for related APIs. Done means the main libraries and other related APIs are deprecated and direct users toward material_ui and cupertino_ui.

Written by the indexing model from the issue text.