Fixes https://github.com/flutter/flutter/issues/4407

Previously it wasn't included in the Runner target.

* Driver commands for controlling the Input widget

This commit introduces two new driver commands for controlling the
material Input widget.

* setInputText(SerializableFinder finder, String text)
* submitInputText(SerializableFinder finder)

Since it is not possible to directly modify the Input widget text,
these driver commands invokes the handler functions of the Input
widget: onChanged and onSubmitted, respectively. The `submitInputText`
command returns the submitted String as a result.

* Make input command handler methods private

Addressing comments from @yjbanov.

Simplify iOS template project

Fall back to the default xcodeproj if a workspace cannot be found

Remove dependency on FlutterAppDelegate so devs can more easily add SDKs.

When using flutter run, build the workspace instead of the project.

* configs for firebase hosting

* use the implicit FIREBASE_TOKEN

* don't print every command (lowers the chance of printing secret env vars, and for realz only deploy when merging into master

Previously adding the GridPaper caused us to lose all the state in our app. Now
we use a global key to keep our state.

Fixes #4648

Putting the opacity in the color is much faster than using an opacity
widget because the opacity widget creates an offscreen buffer.

Fixes #4651

Previously we triggered an assert.

Fixes #4850

We were stacking up two dismiss timers. Now we don't start a new timer
if we've already got one. Also, fix an animation leak caught by the
test.

Fixes #4640

Rather than requiring the developer to specify a full Decoration, we now
just take an ImageProvider for the thumb image. Also, fix
ImageFit.scaleDown to actually work.

Fixes #4571
Fixes #4673

Also, fix an animation leak found by the test.

Fixes #4619

We now have an EdgeInsets.along function that projects the padding onto the
given Axis rather than repeating this function in several places.

We want to use the FlutterViewController in this new project template.

Fixes #4840

* Make the size setter on RenderBox protected to avoid setting from
   outside the class.
 * Make normalize on BoxConstraints always return an object that
   isNormalized.

Fixes #4761

Bump Dart SDK to `1.18.0-dev.4.0`.