…ap` to typesafe structures. (#7703)

Convert `PatternItem` and `Cap` from JSON wrappers to typesafe classes.

flutter/flutter#155121

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to the [pub versioning philosophy], or this PR is [exempt from version
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<!-- Links -->
[Contributor Guide]:
https://github.com/flutter/packages/blob/main/CONTRIBUTING.md
[Tree Hygiene]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Tree-hygiene.md
[relevant style guides]:
https://github.com/flutter/packages/blob/main/CONTRIBUTING.md#style
[CLA]: https://cla.developers.google.com/
[Discord]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Chat.md
[linked to at least one issue that this PR fixes]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Tree-hygiene.md#overview
[pub versioning philosophy]: https://dart.dev/tools/pub/versioning
[exempt from version changes]:
https://github.com/flutter/flutter/blob/master/docs/ecosystem/contributing/README.md#version
[following repository CHANGELOG style]:
https://github.com/flutter/flutter/blob/master/docs/ecosystem/contributing/README.md#changelog-style
[exempt from CHANGELOG changes]:
https://github.com/flutter/flutter/blob/master/docs/ecosystem/contributing/README.md#changelog
[test-exempt]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Tree-hygiene.md#tests

…o typesafe subclasses (#7699)

`BitmapDescriptor` is currently just a wrapper around JSON, with the
exception of two of its subclasses. This converts all cases to typesafe
structures without breaking the current API.

Part of flutter/flutter#155122

## Pre-launch Checklist

- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [Tree Hygiene] page, which explains my
responsibilities.
- [x] I read and followed the [relevant style guides] and ran the
auto-formatter. (Unlike the flutter/flutter repo, the flutter/packages
repo does use `dart format`.)
- [ ] I signed the [CLA].
- [x] The title of the PR starts with the name of the package surrounded
by square brackets, e.g. `[shared_preferences]`
- [x] I [linked to at least one issue that this PR fixes] in the
description above.
- [x] I updated `pubspec.yaml` with an appropriate new version according
to the [pub versioning philosophy], or this PR is [exempt from version
changes].
- [x] I updated `CHANGELOG.md` to add a description of the change,
[following repository CHANGELOG style], or this PR is [exempt from
CHANGELOG changes].
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel
on [Discord].

<!-- Links -->
[Contributor Guide]:
https://github.com/flutter/packages/blob/main/CONTRIBUTING.md
[Tree Hygiene]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Tree-hygiene.md
[relevant style guides]:
https://github.com/flutter/packages/blob/main/CONTRIBUTING.md#style
[CLA]: https://cla.developers.google.com/
[Discord]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Chat.md
[linked to at least one issue that this PR fixes]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Tree-hygiene.md#overview
[pub versioning philosophy]: https://dart.dev/tools/pub/versioning
[exempt from version changes]:
https://github.com/flutter/flutter/blob/master/docs/ecosystem/contributing/README.md#version
[following repository CHANGELOG style]:
https://github.com/flutter/flutter/blob/master/docs/ecosystem/contributing/README.md#changelog-style
[exempt from CHANGELOG changes]:
https://github.com/flutter/flutter/blob/master/docs/ecosystem/contributing/README.md#changelog
[test-exempt]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Tree-hygiene.md#tests

…ter in GoRouter (#7752)

The `GoRouter` constructor parameter `routerNeglect` currently has no effect. This PR provides an implementation for this parameter, in line with the original implementation, i.e. _"This will suppress history for all navigation made using go_router"_.

*List which issues are fixed by this PR. You must list at least one issue.*
* flutter/flutter#119398

Updates the Pigeon definition to uses non-nullable generics now that it's possible.

In practice for this plugin it's currently a no-op: the only affected collection is passed from Dart to native, on the Dart side the source was already a `Map<String, String>`, and on the native side we are using languages without nullability support in generics (Java and Obj-C). However, doing this now eliminates tech debt, and will avoid problems if/when the native side switches to Kotlin/Swift.

On iOS, also removes a class that was accidentally left, unused, in the Pigeon definition file after an earlier update to that file. Current versions of Pigeon would generate that class even though it's not used, so removing it from the definition avoids changes to the generated code that would otherwise have been caused by the update.

Part of flutter/flutter#155891

Now that `stable` requires AGP 7.0, which in turn requires Java 11+, we should be able to set our compatibility version to 11 (setting the min Flutter SDK version to current stable).

Also removes the gradle conditionals for setting namespace (and the repo tool checks that it is present), as that was only needed for AGP 4.1 compatibility.

Part of flutter/flutter#156111

This PR introduces a tolerance for rfw material widget tests to fix the golden test error in flutter/flutter#151611.

Part of a fix for flutter/flutter#151659.

Removes workarounds for previous lack of non-nullable generics support. There are no native code changes because in practice we already didn't want nullable values in the collection, we just couldn't express it formally.

Part of flutter/flutter#155891

Updates the Pigeon definition to uses non-nullable generics now that it's possible.

In practice for this plugin it's currently a no-op: the only affected collection is passed from Dart to native, on the Dart side the source was already a `List<String>`, and on the native side we are using languages without nullability support in generics (Java and Obj-C). However, to do this now eliminates tech debt, and will avoid problems if/when the native side switches to Kotlin/Swift.

The Android implementation required some non-trivial changes to adapt to an earlier Pigeon change that we hadn't picked up yet, which was the change from `Result<Void>` (which turned out to be incompatible with Kotlin) to the separate `VoidResult` class.

Part of flutter/flutter#155891