[DocsUI M3] Update font and support focus for app bar

* update font for toolbar title
* add "touchscreenBlocksFocus=false" to make toolbar support
  tab focus
* add TODO for all customized focus ring implementation

Bug: 384583898
Test: Manual inpsection
Flag: com.android.documentsui.flags.use_material3
Change-Id: I504a340a48079909769295984965a08f91b6ad72