Corects a bnuch of typeos throuhgout teh Fluter codebsae.

Made use of the `misspell` tool:
https://github.com/client9/misspell

Reland: Ensure that flutter run/drive/test/update_packages only downloads required artifacts  (#30254)

Revert "Ensure that flutter run/drive/test/update_packages only downloads required artifacts (#30075)" (#30232)

This reverts commit e38be671.

* add trailing commas on list/map/parameters

* add trailing commas on Invocation with nb of arg>1

* add commas for widget containing widgets

* add trailing commas if instantiation contains trailing comma

* revert bad change

* enable lint unnecessary_new

* fix tests

* fix tests

* fix tests

We were already skipping the check in `flutter upgrade` but this also spawns `flutter precache` and `flutter doctor` which would still check and potentially output the message.

* Try to make transitioning channels actually work.

* Update upgrade.dart

Generate the "version" file from git tags.
Remove the old VERSION file and mentions of versions in pubspec.yaml files.
Replace the old update_versions.dart script with a new roll_dev.dart script.
Update "flutter channel".
Update "flutter upgrade", including making it transition from alpha to dev.
Update "flutter --version" and "flutter doctor".

Adds a class `PubContext` with a fixed set of allowed values
Make it clear these values should not be changed casually

Fixed one inconsistency already: update_packages vs update_pkgs
Provide more information for verify calls
Eliminate `ctx_` prefix.

* Provide more information in PUB_ENVIRONMENT for `pub get/upgrade`

Should help diagnose and fix https://github.com/dart-lang/pub-dartlang-dart/issues/636

`adb` can sometimes hang, which will in turn hang the Dart isolate if
we're using `Process.runSync()`. This changes many of the `Device` methods
to return `Future<T>` in order to allow them to use the async process
methods. A future change will add timeouts to the associated calls so
that we can properly alert the user to the hung `adb` process.

This is work towards #7102, #9567

Fixes https://github.com/flutter/flutter/issues/9258

* Avoid downloading artifacts twice

* Don't update cache before `flutter upgrade` is executed (`flutter upgrade` might bump the engine version)
* Don't update cache twice during `flutter precache`

Fixes #8249.

* add test

Stop building (unused) unlinked summaries for packages.

Improves update speed considerably (for `n` packages it saves us `n` needless calls to `pub get`).

* Remove the workaround that pinned args to v0.13.6
This reverts most of the changes in commit 6331b6c8
* throw exception if exit code is not an integer
* rework command infrastructure to throw ToolExit when non-zero exitCode
* convert commands to return Future<Null>
* cleanup remaining commands to use throwToolExit for non-zero exit code
* remove isUnusual exception message
* add type annotations for updated args package

* convert pubGet to throw ToolExit on non-zero exit code
* convert commandValidator to throw ToolExit for non-zero exit code
* convert flutter commands to throw ToolExit for non-zero exit code
* use convenience method throwToolExit
* only show "if this problem persists" for unusual exceptions

Ensure that any new/changed doctor checks are evaluated and reported
post upgrade.

* refactor _run to runCmd

* replace requiresProjectRoot getter with call to commandValidator

* replace requiresDevice getter with call to findTargetDevice

* trace command requires a debug connection, not a device

* inline androidOnly getter

* rename command methods to verifyTheRunCmd and runCmd

* move common verification into BuildSubCommand

* rename deviceForCommand to device

* rename methods to verifyThenRunCommand and runCommand

* Build unlinked summaries for packages on upgrade.

* Iterate through the packages in folders.

* Rollback the debug change.

To avoid orphaning people on the deprecated alpha branch, this patch teaches
`flutter upgrade` to switch to the master branch.

* implement flutter packages get/upgrade command
* alias flutter pub
* refactor findProjectRoot for use by multiple commands

fixes https://github.com/flutter/flutter/issues/4994

* enhance flutter upgrade to find project root
fixes https://github.com/flutter/flutter/issues/2990

* address comments

* restore original formatting

* fix lints

* Fix `flutter upgrade`

* Fix builds on iOS