UWP apps must be launched using their package family name, but are
uninstalled using their full package name. This patch updates the
Application class to store both.

Further, when launching UWP apps, we now do a lookup to verify the
package exists before attempting to launch it.

Replaces manual registry crawling with a lookup via
Windows.Management.Deployment.PackageManager. This eliminates the need
for the Registry class.

Covered by existing tests.

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

This appears to have triggered reproducible failures in channels_integration_test_ios:

    [   +4 ms] 00:01 [32m+0[0m: channel suite step through[0m
    [+3744 ms] Unsupported value: Sun Mar 11 07:16:42 2018 of type __NSTaggedDate
    [        ] *** Assertion failure in void WriteValue(CFMutableDataRef, id)(), FlutterStandardCodec.mm:340
    [   +2 ms] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Unsupported value for standard codec.'
    [        ] *** First throw call stack:
    [        ] (0x19d5bd9d8 0x1b1940b54 0x19d4cc50c 0x19e815238 0x1050031ec 0x104823f80 0x105003aac 0x1050009bc 0x104824e9c 0x105000b4c 0x104d0cc98 0x10501b398 0x104fb3c94 0x104fb72c4 0x19d53e3e0 0x19d53dfe4 0x19d53d4c4 0x19d537850 0x19d536ba0 0x1b429c598 0x19fe282f4 0x19fe2d874 0x1048257fc 0x19d215568)
    [        ] libc++abi.dylib: terminating with uncaught exception of type NSException
    [  +65 ms] Process 541 stopped
    [        ] * thread #1, queue = 'com.apple.main-thread', stop reason = signal SIGABRT
    [        ]     frame #0: 0x00000001c93e584c libsystem_kernel.dylib`__pthread_kill + 8
    [        ] libsystem_kernel.dylib`__pthread_kill:
    [        ] -> 0x1c93e584c <+8>:  b.lo   0x1c93e5868               ; <+36>
    [        ]    0x1c93e5850 <+12>: stp    x29, x30, [sp, #-0x10]!
    [        ]    0x1c93e5854 <+16>: mov    x29, sp
    [        ]    0x1c93e5858 <+20>: bl     0x1c93c2f5c               ; cerror_nocancel
    [        ] Target 0: (Runner) stopped.

Example builds:
* https://ci.chromium.org/ui/p/flutter/builders/prod/Mac_ios%20channels_integration_test_ios/828/overview
* https://ci.chromium.org/ui/p/flutter/builders/prod/Mac_ios%20channels_integration_test_ios/829/overview
* https://ci.chromium.org/ui/p/flutter/builders/prod/Mac_ios%20channels_integration_test_ios/830/overview
* https://ci.chromium.org/ui/p/flutter/builders/prod/Mac_ios%20channels_integration_test_ios/831/overview

Example Log:
* https://logs.chromium.org/logs/flutter/buildbucket/cr-buildbucket.appspot.com/8847377106855056784/+/u/run_channels_integration_test_ios/stdout

This reverts commit 99021da0.

UWP apps get a single arguments string on launch rather than an array.
The current implementation splits that args string on commas. This
updates the UWP launch args generation to match.

Part of https://github.com/flutter/flutter/issues/81756
Part of https://github.com/flutter/flutter/issues/82085

Also adds some user-friendly messages to stderr to aid with any
debugging, and emits the PID to stdout.

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

Sped up the StandardMessageCodec for iOS, tiny tweaks about 5% gain.

In each library where an import is removed, the library uses some elements
provided by the import, BUT there is another import which provides all of the
same elements, and at least one more which the library uses.

In this change, we remove the imports which can be simply removed in favor of
the other already present imports.

See https://github.com/dart-lang/sdk/issues/44569 for more information.

https://skia.googlesource.com/skia.git/+log/c1b6b6c615a7..d9a7c5953df3

2021-05-12 skia-autoroll@skia-public.iam.gserviceaccount.com Roll Chromium from 5d4a69b076e1 to 51f0f14b5681 (472 revisions)
2021-05-12 skia-autoroll@skia-public.iam.gserviceaccount.com Roll Dawn from e2f083e4b0f5 to f0fdfa0d61df (1 revision)

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/skia-flutter-autoroll
Please CC robertphillips@google.com on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+doc/master/autoroll/README.md

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