automatically focus the first row/panel/key on first render and after making selections

[kshen0]

Overview

Small QOL change for the switch scanning keyboard for write-ins

• Focus the first row when the keyboard is first rendered
• After a row/panel/key is selected, focus the first child
  • Row selected -> focus first panel
  • Panel selected -> focus first key

Demo Video or Screenshot

scan-panel-write-ins-autofocus.mov

Testing Plan

Updated existing tab/enter test to expect focus without tabbing

Checklist

• I have added logging where appropriate to any new user actions, system updates such as file reads or storage writes, or errors introduced.

• I have added a screenshot and/or video to this PR to demo the change
• I have added the "user_facing_change" label to this PR to automate an announcement in #machine-product-updates

[kofi-q]

🎉