Fixes #10929

* Add hasAGoodToStringDeep and equalsIgnoringHashCodes methods.

Methods simplify testing of toStringDeep calls and other cases where
methods return strings containing hash codes.

This allows us to take advantage of improved command-line tooling (e.g.,
improvements in device listing in Instruments). Now that the engine is
built with Xcode 8 and the framework is tested against Xcode 8, this
reduces the set of configurations we need to support to allow us to
focus on the supported ones: Xcode 8 and Xcode 9.

...and make one of the comments accurate by fixing the code. Turns
out I forgot to add the 'silent' argument when I changed that comment.

This print statement provides no value to the user.

https://github.com/flutter/flutter/issues/10940

The upstream fix is: https://github.com/dart-lang/usage/commit/021664efd35d563ee21eadbed40af6b5e8e23b2e

* Revert "Revert "Change all ocurrences of '$runtimeType#$hashCode' to use the idAndType method. (#10871)" (#10880)"

This reverts commit ceb814aa.

Revert "Change all ocurrences of '$runtimeType#$hashCode' to use the idAndType method. (#10871)" (#10880)

This reverts commit d46e208b.

* Change all instances of '$runtimeType#$hashCode' to use the describeIdentity method.

The describeIdentity method generates a shorter description with a consistent length
consisting of the runtime type and the a 5 hex character long truncated
version of the hash code.

(The Flutter plugin will use this to update the UI with test progress.)

Going forward, Android support libraries are published on maven (instead of bundling them with the SDK). Many plugins depend on these. To avoid requiring plugin users to add the maven repository to their app this change adds the repository to the template for `flutter create`.

This also bumps the support-annotations dependency to 25.4.0 (which also requires the new maven repository).

Fixes https://github.com/flutter/flutter/issues/10541

* Add version information to dartdoc footer

* Add final to variable declaration

* Drop toString()

Remaining known issues are #10831 and #10830.

Fixes https://github.com/flutter/flutter/issues/10703

Introduce CompositedTransformTarget and CompositedTransformFollower
widgets, corresponding render objects, and corresponding layers.

Adjust the way text fields work to use this.

Various changes I needed to debug the issues that came up.

* send channel name as a custom dimension

* tweaks from review

* remove unused import

Replace use of ideviceinfo in devicelab tests with Xcode instruments
lookup.

This libimobiledevice tool is no longer used anywhere in the flutter_tools codebase.

This reverts commit b2909a24.

This resubmits the following patches:

1. Use Xcode instruments to list devices (#10801)
Eliminates the dependency on idevice_id from libimobiledevice. Instead,
uses Xcode built-in functionality.

2. Make device discovery asynchronous (#10803)
Migrates DeviceDiscovery.devices and all device-specific lookup to be
asynchronous.