Add additional tests for classes in package avrcpcontroller

This CL adds tests for:
- AvrcpItem
- AvrcpCoverArtStorage
- BipImageDescriptor
- BipAttachmentFormat
- BipImageFormat
- BipDatetime

Bug: 237467631
Test: Ran each test with atest
Change-Id: I2fac97ccc63c5368ab1fb731041adb50fcc559ea
(cherry picked from commit af325133)