Finalize Component2 API - part 2 of X

[greglittlefield-wf]

Motivation

Component2 was implemented via a large number of PRs, and has some parts that need to be cleaned up before release.

Changes

• Component2Bridge
  • Rename Component2Adapter -> Component2Bridge (a better description of the design pattern it uses)
  • Move into its own file
  • Use Expando for storing it so that it isn't part of Component's public API
  • Add stub for jsifyPropTypes (to be consumed in @kealjone-wk's PR)
  • Allow injection of custom bridge implementations within registerComponent2
• Re-wire up registerComponent2 since we will need it after all to be able to inject custom bridges
• Clean up and document JSBackedMap implementation
  • Make it always Map<dynamic, dynamic> since we can't trust that the keys/values coming from the JS map match the type parameters the consumer might use
• Misc cleanup
  • Make some interop-related members added in 5.1.0-wip visibleForTesting
  • Add some missing deprecations to JS interop files
  • Remove unused bind-related APIs

Boyscouting

• Ignore deprecations from current package to cut down on lints
• Fix miscellaneous lints, including removing unused code
• Rename unexported Ref typdef that conflicted with the new Ref type, which was confusing and made imports messy
• Make _ReactDartInteropStatics2 a class with static methods instead of a closure,
  • Is cleaner, more grokkable, and easier to work with in IDEs
  • Removes the need for a JS interop class that mirrors all of the function types for type safety

Testing

• CI passes
• Examples still work

[kealjones-wk]

+10