We now have 100% coverage of animation.dart and animation_controller.dart.
Also, add some basic tools for working with lcov files. These tools need much
more polish.

Uploading the coverage data file to Google Storage will make it easier
for folks to get current coverage data quickly.

Update to latest analyzer (0.27.4-alpha.14) and misc. analysis fixes.

It's not reliable enough yet.

Also, fix the bug where apps would assert when you change the time dilation.
Use that mechanism to fix the animation controller tests.

#4672

This patch causes us to upload a coverage report to coveralls.io.

* brings in analyzer version (`0.27.4-alpha.14`) corresponding to current Dart SDK (`1.18.0-dev.2.0`).
* updates analysis to use prefered API for embedder URI resolution
* adds trampolines to `State` and `StatelessWidget` to allow for warning-free within-library @protected access (needed since we closed off access to @protected closures from outside subclasses).
* turns off cache dependency tracking for analysis (in DDC this amounted to a 10% speed improvement).

We need https://github.com/dart-lang/coverage/issues/100 to be fixed before
this will be useful.

Fixes #2342

Bump Dart SDK to `1.18.0-dev.2.0`.

This API is the front-end part of the work on showing licenses.

Future patches will:

* Provide an API for registering what licenses should be shown here,
  which will be used by this feature to shown licenses but could also be
  used by custom code for showing licenses (e.g. for people not using
  the Material widgets).

* Actually populate this license API from all the licenses we currently
  use in the engine, in the framework, and from any pub packages that
  are used (directly or indirectly) by the application.

Gets a bunch of fixes.  Most notably a VM that has background compilation re-enabled (and stable).  This should win us (back) a ~17% improvement of analysis times (CLI and server).

See: https://github.com/dart-lang/sdk/issues/26697 for more context.

I erroneously removed this function in an earlier patch. Also, export
SystemUiOverlayStyle because we expose that enum in the SystemChrome
API.

This required switching from the Future-based bindings to the callback-based
bindings.

This is now obsolete

The error code path wasn't actually getting the point where it would throw the
useful error message. Also, fix error recovery when runApp fails.

Fixes #4655

* Fixing sprites' image map regression.
* Smoke tests for ImageMap

* Only schedule overlay style update microtask if needed

* Simplify API

Anywhere that accepted IconData now accepts either an Icon or an
ImageIcon.

Places that used to take an IconData in an `icon` argument, notably
IconButton and DrawerItem, now take a Widget in that slot. You can wrap
the value that used to be passed in in an Icon constructor to get the
same result.

Icon itself now takes the icon as a positional argument, for brevity.

ThemeData now has an iconTheme as well as a primaryIconTheme, the same
way it has had a textTheme and primaryTextTheme for a while.

IconTheme.of() always returns a value now (though that value itself may
have nulls in it). It defaults to the ThemeData.iconTheme.

IconThemeData.fallback() is a new method that returns an icon theme data
structure with all fields filled in.

IconTheme.merge() is a new constructor that takes a context and creates
a widget that mixes in the new values with the inherited values.

Most places that introduced an IconTheme widget now use IconTheme.merge.

IconThemeData.merge and IconThemeData.copyWith act in a way analogous to
the similarly-named members of TextStyle.

ImageIcon is introduced. It acts like Icon but takes an ImageProvider
instead of an IconData.

Also: Fix the analyzer to actually check the stocks app.