Update Material tokens to 0.162

* Fix typos

* lowercase animated & opacity

* Undo typo fix

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Co-authored-by: Michael Goderbauer <goderbauer@google.com>

* Update to v0.158 of the token database.

* Update checkbox template

* Fix DatePickerTheme test

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Co-authored-by: Qun Cheng <quncheng@google.com>

* dart fix --apply

* manual fixes

* Updated to tokens v0.150.

* Updated with a reverted list_tile.dart.

* Enable  lint

* note about discarded_futures

* note about use_decorated_box

* update note on require_trailing_commas

Add `indicatorColor` & `indicatorShape` to `NavigationRail`, `NavigationDrawer` and move these properties from destination to `NavigationBar` (#117049)

* Add `IndicatorShape` to `NavigationRailTheme` and fix  indicator ripple.

* remove unused variables

* Added SafeArea for NavigationRail
Co-authored-by: Qun Cheng <quncheng@google.com>

Refactor gen_defaults to support multiple generated code blocks in the same file independently. (#107278)

* Improve `useMaterial3` documentation

* reverse styles and components

* tweak language around support

* Update theme_data.dart

* remove trailing space

* Update packages/flutter/lib/src/material/theme_data.dart
Co-authored-by: Darren Austin <darren@darrenaustin.org>

* add missing spec links

* remove spec links from useMaterial3

* move defaults section up, rejig things

* spaces no longer trailing

* spaces no longer trailing (2)
Co-authored-by: Darren Austin <darren@darrenaustin.org>

* Use `curly_braces_in_flow_control_structures` for `material`

* include test/material

* add back removed comments

This reverts commit 5fd259be.

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 adds a smoke test for every single API example. It also fixes 17 tests that had bugs in them, or were otherwise broken, and even fixes one actual bug in the framework, and one limitation in the framework.

The bug in the framework is that NetworkImage's _loadAsync method had await response.drain<List<int>>();, but if the response is null, it will throw a cryptic exception saying that Null can't be assigned to List<int>. The fix was just to use await response.drain<void>(); instead.

The limitation is that RelativePositionedTransition takes an Animation<Rect> rect parameter, and if you want to use a RectTween with it, the value emitted there is Rect?, and one of the examples was just casting from Animation<Rect> to Animation<Rect?>, which is invalid, so I modified RelativePositionedTransition to take a Rect? and just use Rect.zero if the rect is null.