send back Widget class name information in the widget rebuild/repaint count event

Fixes https://github.com/flutter/flutter/issues/81587

* Add connectedVmServiceUri service extension and set from flutter_tools

* Create custom DiagnosticsNode type for DevTools deep links.

* Enable structured errors by default.

Fix assert due to VSCode passing in an isolateId as well as the expected args to setPubRootDirectories. (#68721)

* Fix null safety error in inspector service extensions taking variable numbers of args.

Fixes https://github.com/flutter/flutter/issues/68627.
Also fix all inspector tests that do not rely on golden image functionality
so that they run with --enable-experiment=non-nullable. This verifies there
is test coverage to ensure there isn't a regression.

* Remove uses of dynamic.

* apply upcoming lint cast_nullable_to_non_nullable

* make RenderObjectElement.renderObject non-nullable

* Reland "Nnbd widgets (#64672)"

This reverts commit 127e6790.

* remove non-nullable enforcement on AsyncSnapshot

* make data param non-nullable for AsyncSnapshot.withData

* make some Text params non-nullable

This reverts commit e682ec71.

* migrate widget to nullsafety

* remove double blank line after license

* address review comments in actions.dart

* nullable ObjectKey.value

* use local variable oldElement

* make State.build non-nullable

* make State.context non-nullable

* newline at eof

* make ProxyWidget.child non-nullable

* make _InactiveElements.debugContains non-nullable

* make Element.depth non-nullable

* make ProxyElement.build non-nullable

* make StatefulElement.state non-nullable

* remove 'Notice that'

* avoid cast of list in RenderObjectElement.updateChildren

* make IndexedSlot.value non-nullable

* avoid cast of list in MultiChildRenderObjectElement.mount

* make some WidgetsApp parameters non-nullable

* hitTest take non-nullable position

* make ScrollableState.position non-nullable

* use _pixels instead of pixels

* make ViewportOffset.pixels non-nullable

* make param and return type of IndexedWidgetBuilder non-nullable

* unused_import

* make context param non-nullable for Builder in animated_list.dart

* make ScrollMetrics.viewportDimension non-nullable

* make ScrollMetrics.{min,max}ScrollExtent non-nullable

* make _Location.file non-nullable

* _WidgetForTypeTests.createElement throw UnimplementedError

* update _NullWidget.build error message

* make _ShortcutsState.manager non-nullable

* Fix childCount issues for NNBD

* fix childCount computation on web

* increase max value on js side to compute childCount

* make aspect parameter of dependOnInheritedWidgetOfExactType nullable

* merge has{min,max}ScrollExtent into hasScrollExtents

* update focus_manager.dart

* address review comments in icon.dart

* address review comments in image.dart

* address review comments in routes.dart

* address review comments in scroll_activity.dart

* update doc comments

* make UserScrollNotification.direction non-nullable and required

* rename hasScrollExtents to hasContentDimensions

* unnecessary late
Co-authored-by: Ian Hickson <ian@hixie.ch>

* add language version 2.8 in packages/flutter

* enable non-nullable analyzer flag

This reverts commit f0174b17.

* Revert "Revert "Send text error in JSON and print in tools (#58284)" (#58872)"

This reverts commit c2d5e18c.

* Put streamListen in try/catch if extension events already listened for