Add wearable earbud appearance support

This value is defined in the "Appearance Value" specification, and the revision date is
2021/04/20. Add this value support to identify earbuds for LE audio
use case. During the discovery process, the UI can display appropriate icons.

Bug: 150670922
Test: Scan device and check the icon.
Change-Id: I2fa61e9fd96581cd08b1966df267eefcf69ab914