Fixes #8519

The latter is the proper spelling.

Fixes #8883

We keep breaking --watch because we don't test it.

Fixes #7520

Fixes #4017

Previously they tried to compute an integer target end index, but
integers can't represent infinity. Now we use null to represent
infinity.

Also, fix some similar issues with grids.

Fixes #8398

Fixes #7503
Fixes #8870

* Remove legacy .apk build.

Print out an error message telling the user to upgrade the project if
it's not Gradle-based. Removed all the obvious traces of the legacy
build.

Added support for Dart VM kernel snapshots in Gradle builds.

Fixed Android installs to verify that the app is actually installed, and
not just rely on the presence of the .sha1 file.

Fixes #4301

The recommended minimum tappable area is actually 44.0pt according to the [iOS Human Interface Guidline](https://developer.apple.com/ios/human-interface-guidelines/visual-design/layout/).

> Provide ample spacing for interactive elements. Try to maintain a minimum tappable area of 44pt x 44pt for all controls.

I've also added an override to allow for flexibility in situations where designers get naughty and have a desire to make everything super small.

This update adds support for custom fonts in icons. As an example, it
can be used with the icon-set from https://materialdesignicons.com

Thanks to @vlidholt for the original patch.

Fixes #4494
Fixes #3199

Fixes #7793.

This machinery is useful for arbitrary boxes (e.g., with FittedBox).

Fixes #6463

Fixes #6382

The excellent `local-history` plugin for vscode, saves history in `.history` files; this ignores them.

See: https://marketplace.visualstudio.com/items?itemName=xyz.local-history

Fixes: #8783

Fixes #8850

Breaking change: removed deprecated methods of PlatformMessages, leaving only binary messaging there. All other use of platform communication now goes through PlatformMessageChannel and PlatformMethodChannels. Retained use of String and JSON codecs for now.

Companion engine PR: flutter/engine#3482

Fixes #8821

The problem has been fixed upstream in the Dart VM.

This simplifies our setup instructions on Windows (will update the wiki).
Furthermore, this also means that going forward there is no diffrence between PowerShell and Cmd for the Flutter experience on Windows.

Function keys don't work great on any platform we support:
* Mac doesn't have first-class function keys.
* On Ubuntu: F1 opens the system help and F10 opens the file dialog.
* ... and Windows is a mess as well.

It's no longer needed with the latest Dart SDK roll.