Task/Issue URL: https://app.asana.com/1/137249556945/project/608920331025315/task/1211407036705136?focus=true

Description

Adds JS->native communication so we know which step of the automated Takeout flow we're on at any given time. The primary use case for this will be in a later PR around cancellation so there's not much to see in terms of changes in this PR.

Steps to test this PR

Logcat filter: Bookmark-import:

Test success, steps communicated

• Fresh install internal build type
• Visit Autofill Dev Settings and choose to Launch Bookmarks Import Flow
• You'll see the sign in page; verify in logs you see latest step is: login-first
• Sign and let the automation carry on. Verify you see a bunch of steps being notified as it goes.
• Allow it to complete, and verify in the last few steps you see download-detected and completed-successful

Test cancellation

• choose to Launch Bookmarks Import Flow again
• while it is showing the in-progress view, tap the X and confirm you want to cancel
• verify you see in the logs cancelled at stage: (where the value will vary based on when you cancelled it)

Test error encountered in step processing

• Apply patch which will simulate an error step
• Tap on Launch Bookmarks Import Flow and wait for the simulated error to happen
• Verify you see the error screen
• Verify in the logs you see Import failed with reason: WebAutomationError(step=bookmark-modal-expectation)