Make Element tree root generic

Convert `AndroidSemanticsAction` to enum.

This reverts commit 275ab9c6.

Revert "Reland "Remove references to Observatory (#118577)""

This reverts commit 298d8c76.

* Fix typos

* lowercase animated & opacity

* Undo typo fix

---------
Co-authored-by: Michael Goderbauer <goderbauer@google.com>

* lerp documentation

* Remove Note, Note That from repo

* Improve BorderSide documentation.

* apply review comments

This reverts commit 2df140f4.

* Add `@widgetFactory` annotation

* Simplify and fix example

* Specify `TargetKind`s for `widgetFactory`

* Explain why `library_private_types_in_public_api` is ignored.

* Trigger CI

Observatory is being deprecated for Dart 3.0 so it should no longer be
referenced in tooling messaging / flags.

See https://github.com/dart-lang/sdk/issues/50233

* add failing test

* fix

* remove extra whitespace

* fix test failure

* disable trackrebuilddirtywidgets in teardown

* remove no-shuffle annotation

* fix

* dart fix --apply

* manual fixes

Changes our inspection behaviour so that it also sends a postEvent on the ToolEvent stream.

* Revert "Revert "Remove single-view assumption from widgets library (#117480)" (#117545)"

This reverts commit b8d5d9c4.

* check for mounted

This reverts commit b8b35671.

* Fix LayoutExplorer cycle

* fix tests

* Update widget_inspector.dart

* Update widget_inspector.dart

* review

* expandPropertyValues

The pubRoot directory interface is being changed to promote adding and removing directories

* more const immutable classes

* more const constructors in dev/ and examples/

* Use `curly_braces_in_flow_control_structures` for `widgets`

* fix comments

* fix comments

add noSuchMethod to _MulticastCanvas to unblock smoke testing against forthcoming new getTransform/Clip methods (#103737)

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