This commit contains:

- FlutterDriver API for e2e tests usable in conjunction with package:test
- FlutterDriverExtension to be enabled by the application in order to
  allow an external agent to connect to it and drive user interactions and
  probe into the element tree
- initial implementations of tap, findByValueKey and getText commands (to
  be expanded in future PRs)

Added a few operators to the Velocity class.

#1968

Teach flutter to run from a relative path

Previously we were trying to run pub from the wrong working directory.

Adds dialog for completed workout in Fitness demo

More work on validation

Updated grid.dart

rename some flutter command references in readmes

make the ios development path less mandatory

Revert "iOS: Treat the initial Info.plist string as a mustache templa…

Revert "iOS: Treat the initial Info.plist string as a mustache template and use the project name to initialize the bundle name and identifier"

This reverts commit dd4361bc.

We still use the hard-coded name in a number of places, including
launching the app on the iOS simulator.

Fixes #1950

Update the regex used to filter out Flutter specific logs

Perform an engine version check on start and update the Xcode project if necessary

iOS: Treat the initial Info.plist string as a mustache template and use the project name to initialize the bundle name and identifier

iOS: Treat the initial Info.plist string as a mustache template and use the project name to initialize the bundle name and identifier

Improve error message when Android SDK not found

Also, look for the Android SDK in the default locations.

Added Grid row and column spacing, changed padding interpretation

Grid padding now defines the distance the overall grid is inset. The grid rowSpacing and columnSpacing attributes define the space between rows and columns respectively.

Add iOS configuration files for all examples and remove GN related files

Hide flutter run_mojo

Add iOS specific assets to the Stocks example

Remove flutter ios command

All the functionality of this command has been integrated into other commands.

Refactor: Rename initialize_xcode.dart to setup_xcodeproj.dart

Enforce that we get a final move to the pointer up location

`flutter start` initializes the Xcode project if the user has not already done so.