Landing on red to green the build.

* Use persistent hash map to store _inheritedWidgets

Instead of using a HashMap and copying it down the tree
which leads to quadratic time and space complexity
use a persistent data structure which can amortize
the cost by sharing parts of the structure.

The data shows HAMT based PersistentHashMap to be
5-10x faster for building _inheritedWidgets and
considerably more space effecient (e.g. bringing
amount of memory allocated when constructing
_inheritedWidgets in a tree with 150 InheritedWidget
down to 70Kb from 970Kb).

PersistentHashMap is slower than HashMap for
access: 2-3x in relative terms, but in absolute
terms we are only talking about ~0.2ns slow down
per access and various app benchmarks we run have
have not revealed any significant regressions.

* Sort diagnostics node dependencies so that order is stable

* use toDescription

* use toStringShort when possible

* sort InheritedElements

* Use `curly_braces_in_flow_control_structures` for `widgets`

* fix comments

* fix comments

This reverts commit ec8693e8.

* Added a bool that allows us to limit debugProfileBuildsEnabled to user
created widgets.

* made it turned on by default

* switched to hashmap

* Cleaned everything up and added tests

* fixed an odd test where it wants to be able to add asserts and run in profile mode

* hixie feedback

* hixie2

* made it default to false

* updated docstring as per dans request

* fix deprecated_new_in_comment_reference for `material` library

in a future version of the SDK, these will be flagged, fix them now

* Update pubspec.yaml

* migrates lib/foundation and lib/widgets

* migrates lib/painting and lib/material

* migrates lib/cupertino, lib/gestures, lib/services, lib/semantics and lib/rendering

* fixes failing tests

* migrates test/

* improves hashing of lists