Move OBEX related objects to an OBEX folder and change name scheme

This change restructures our folder heirarchy to have an obex/ folder to
contain the related OBEX request and data objects. It also contains the
OBEX client abstraction in it that the state machine uses to issue OBEX
requests.

Bug: 365626536
Flag: EXEMPT, name changes and file movement only
Test: atest com.android.bluetooth.pbapclient
Test: m com.android.btservices
Change-Id: I2bbb0329a184ebb979599d63c849397c917a663f