Various improvements (in particular a new painting fuzzer) to the text manual test.

Some additional documentation.

A fix to Stack to remove an LTR bias: make unpositioned children apply "alignment".

Some more debugging information on RichText and Text.

A fix to the flutter tool to not crash when an RPC call throws an exception.

* alwaysUse24HourFormat in MediaQuery and time picker

* docs; dead code

* address some comments

* MaterialLocalizations.timeOfDayFormat is the single source of 24-hour-formattedness

* Make TimePickerDialog private again

* wire up MediaQueryData.fromWindow to Window

Other missing dart docs have been added in https://github.com/flutter/flutter/pull/12813.

* Add acceptNotification parameter to RefreshIndicator and OverscrollIndicator

* Various fixes suggested by reviewer

* Fixed lint errors

(in preparation for moving the semantics stuff out of rendering)

* remove locale "sd" (not supported by ICU/CLDR); unify localizations scripts CLI

* address comments

* Add a custom semantics sample

* typo

* Review comments

* Support value announcment for increase/decrease

* ++

* review comments about docs

* fix miscellaneous typos in dartdocs

* moar typos

Fixes https://github.com/flutter/flutter/issues/12460

Previously, the usage analytics would generate a write to the user's
HOME directory during the Fuchsia build. We're tightening down the
environment in which we run the Fuchsia build, and these writes are now
more obvious.

This patch removes the usage analytics during the Fuchsia build,
avoiding the write to the user's HOME directory.

Archive builds for upload to iTunes Connect should always be built in
release mode, not doing so results in crash on startup.

Bug: https://github.com/flutter/flutter/issues/12086

* upgrade intl data; use local numerals in date picker

* use the shiny new public intl API

* address comments

* Revert "Revert "fix --force-upgrade script; upgrade to the latest package versions (#12700)" (#12729)"

This reverts commit 7f0d4f4c.

* keep linter pinned at 0.1.35

* Add option for custom actions to Semantics widget

* review comments

* review comment

* Revert "roll engine (#12660)"

This reverts commit 048bc5e0.

* Revert "FittedBox RTL (#12662)"

This reverts commit 05a22fe0.

* Revert "Revert "nav bar font styles are special, do not inherit (#12578)" (#12661)"

This reverts commit 662b6684.

This reverts commit 5b357500.

* fix updrade script; upgrade to the latest package versions

* exclude special dependencies from transitive closure

* fix stack trace handling in flutter_test due to stack_trace change

* change type on _emptyStackTrace

Use a `package:` import when referencing source under test in test template.

This is the prefered style and plays nice w/ automated refactoring.

See: https://github.com/flutter/flutter-intellij/issues/1429

fixes #11992 

* enable lint prefer_const_constructors_in_immutables

* remove LabeledGlobalKey._

* enable lint prefer_foreach

* fix tests

Use our platform identifiers rather than OS names for the platform
switcher radio buttons in the drawer as noted in section 2.3.10 of the
App Store review guidelines.

See: https://developer.apple.com/app-store/review/guidelines/

* Add a pageSnapping parameter to PageView

Setting the pageSnapping property allows extending the PageView scroll
behavior, such as custom scroll animations or custom scroll bars.

* Apply pageSnapping CR feedback

- Remove _kNonSnappingPhysics, use null instead.
- Minor code style fixes.
- It turns out that the forth state is Arkansas, not California.

This adds an optional character counter and maxLength parameter to the TextField, as described in the Material Design Spec.

The counter text and style in the input decorator may be specified, but will default to the "right thing" if not specified, where the "right thing" is a counter that looks like "3 / 10" (if there are three characters entered into a field where maxLength is set to 10).

To limit the number of characters entered, I created a LengthLimitingTextFormatter that will limit the number of characters (Unicode runes) in the input, which can be used independently. The formatter is applied after the other formatters supplied (if any). Even if there is no decorator, the text field will limit the number of characters input if maxLength is set.

If maxLengthEnforced is set to false (it defaults to true), then the max length will not be enforced. In that case, if the text exceeds the length, then the counter will turn red, and it will make the divider turn red.