Modernize tutorials

[rjrjr]

At long last, the Tutorial catches up with the current release.

• Big picture discussion of our navigation story (see the end of Tutorial2.md)

• Use AndroidScreen and drop ViewRegistry

• Better, more consistent use of BackStackScreen

• Use View.setBackHandler

• Use TextController

• Use RequestContext.eventHandler

• Delete a lot of // Exactly what the function name and the code say comments

• Hint at the existance of ComposeWorkflow and Overlay without turning this into a complete rewrite

• More consistent naming, code style for actions and event handlers in Screen renderings

  • Event handler fields are named onVerbPhrase, like onBackPressed
  • Action names are verb phrases describing the action that is being taken, not the event that is being handled
  • Output names are generally in terms of the semantic event being reported to the parent, rather than describing what the parent will do

Thus:

return TodoListScreen(
  onRowPressed = { context.actionSink.send(reportSelection(it)) }

  private fun reportSelection(index: Int) = action {
    // Tell our parent that a todo item was selected.
    setOutput(TodoSelected(index))
  }

(Although most of these are inlined as eventHandler("…") {} calls.)

I've mainly focussed on updating what exists, not extending its coverage further. Once this is merged I'd like to follow up and do more:

• Introduce Overlay properly
  • How about move TodoEditScreen to a BottomSheetDialog?
  • Could be too noisy, BottomSheetDialog is a bastard.
  • If that's the case create a separate sample for it.
• Introduce Compose.
  • I think the way to go is add a sixth step that updates TodoListScreen, talk about getting rid of that RecyclerView.
  • Could point out that the existing workflows and tests are unchangedn

[rjrjr]

I dropped all the StateFlow declarations because WorkflowLayout.take only requires a Flow, and that's what the navigation logger I add downstream produces.

[rjrjr]

• Requires 1.19.0, fix and wait for that release