Fixes#119401
This PR is to:
* add `Card.filled` and `Card.outlined` factory methods so that we can use tokens for these two types of cards to generate default theme instead of providing hard-corded values in example.
* update card.2.dart example.
* add test file for card.2.dart example.
* fix some mismatch caused by editing the auto-generated defaults by hand in navigation_bar.dart and navigation_drawer.dart.
This does a cleanup of the examples, removing all of the "section" markers and extra comments that we don't need anymore now that the samples are no longer in the source code. It also removes the --template arguments from the {@tool dartpad} and {@tool sample} directives, since those are no longer used. It converts two examples that I discovered were still embedded into linked examples in the examples folder.
I didn't delete the templates from the snippets config folder yet, because there are still embedded samples in the dart:ui package from the engine that use them. Once dart:ui no longer uses the templates, they can be removed.
I bumped the version of the snippets package to pick up a change that allows removal of the --template argument.
This extracts the sample code out from the API doc comments, and places them in separate files on disk, allowing running of the examples locally, testing them, and building of slightly larger examples.
