Update device entry icon label and a11y action

Previously there was no content description so
the device entry icon was announced as unlabled.

Update the a11y action for the device entry
icon to accurately represent a longpress, not
a click.

Fixes: 336313562
Flag: ACONFIG com.android.systemui.device_entry_udfps_refactor NEXTFOOD
Test: manually enable a11y and select device entry icon. observe
the correct label & hint is announced.

Change-Id: I91fef201f56636cdb0c8306a665ab4f6acbadac7