[Auto Pin Confirmation]: Add talkback capability for Auto-confirm correct PIN...

[Auto Pin Confirmation]: Add talkback capability for Auto-confirm correct PIN checkbox even if it is not in focus

- set accessibilityLiveRegion as Polite mode to allow talkback to announce the state of checkbox even if is not in focus

Bug: 281950677
Test: Manual test by flashing on device and checking in talkback mode
Change-Id: Ia1066e2df1f40e6c339a4cd63f92acf0858f8f3d