Re-wrap to 80 columns and use references for style guide links.

Unofficially, this is more about triggering a build than cleaning up.

uwptool is a helper tool used by the flutter command-line tool. It can
be thought of as analogous to adb for Android or libimobiledevice for
iOS.

Its core functions are:
* List installed apps. (included in this patch)
* Launch an app with a set of launch arguments. (included in this patch)
* Install an app (included in a later patch).
* Uninstall an app (included in a later patch).

Part of https://github.com/flutter/flutter/issues/81756

This gets created during vsync and stays for the
lifecycle of the frame.

This reverts commit 304ee816.

* Skip SimpleRasterizerStatistics test on Fuchsia

This test depends on a valid default SkFontMgr to be installed. Otherwise, it uses an empty typeface, which leads to an SkTextBlob with empty bounds and unexpected test failures when Skia updates its quickReject() behavior.

Fuchsia is the only platform that does not install an SkFontMgr.

* Fix code style and line length

* fix race with framework when using tab to traverse in a11y mode

Flutter now covers many non-mobile platforms such as web, desktop, and
embedded scenarios. This updates the introductory text in the README to
match the wording used in the framework README.

This commit is empty and simply triggers a new build to open the tree.

Commit 106963e5 was re-built after a
succesful build; upload to the cloud storage bin failed.

* Revert "Roll Dart SDK from 094c9024373c to 2ea89ef8f6de (1 revision) (#26030)"

This reverts commit 0d62a560.

* Revert "Roll Dart SDK from 04e55dad908d to 094c9024373c (1 revision) (#26027)"

This reverts commit 06cbf1e0.

* Revert "Roll Dart SDK from b4210cc43086 to 04e55dad908d (2 revisions) (#26020)"

This reverts commit d1a11828.

* Revert "Roll Dart SDK from 86c749398b3a to b4210cc43086 (2 revisions) (#26006)"

This reverts commit 3ffb8efc.

* Revert "Roll Dart SDK from b8f4018535fa to 86c749398b3a (16 revisions) (#25999)"

This reverts commit a712ffe2.

The Windows registry is structured as a hierarchy of named keys, each of
which may contain a set of named values of various datatypes.
RegistryKey objects own the underlying HKEY handle and ensure cleanup at
or prior to destruction.

This adds a RegistryKey class that does automatic resource management
for registry keys and provides convenience functions for accessing keys
and navigating the key hierarchy.

This is library code to be used in uwptool, which adds an adb-like
helper tool for install, uninstall, and launch of UWP applications for
Windows platforms.

See: https://github.com/flutter/flutter/issues/81756