* Remove nullOk from cupertino color resolution

* Add CupertinoDynamicColor.maybeResolveFrom

* Remove CupertinoDynamicColor.maybeResolveFrom again

* Add a code sample for the [Offstage] widget

We are standardizing around the term Raw for lower level widgets.

* [flutter_tools] Support zipped application bundles for macOS

It is not possible to directly produce a directory (.app) in some build systems
but rather it must be zip'ed before being passed to the tool for
running. This adds support for attempting to extract an application
bundle from a zip file if the bundle is not already a directory. This
uses very similar code from lib/src/application_package.dart which is
used for extracting an ipa for iOS.

This introduces tests for the macos/application_package.dart behavior which did not exist before. These tests cover the changes in the PR and some of the existing behavior, but do not cover everything in that file.

* Fix failing tests from introducing raw string generation in gen_l10n tool

My yearly pass to fix spelling errors in the API dartdocs.

* start and stop chromedriver once per sub-shard; do not wait for it to quit

* enable web_long_running_tests but keep them as flaky

* [null-safety] enable null safety

* opt expression evaluation web test out of null safety

Disable null safety auto-detection for the web