Pass SessionHandle to UWB Service when opening a session

Instead of having the UWB Service generate a SessionHandle for each
call to IUwbAdapter#openRanging, now the framework must select and
pass in a SessionHandle. This helps to improve consistency across the
API surface and simplifies the implementation of
IUwbAdapter#openRanging.

Bug: 179273688
Test: atest UwbManagerTests
Change-Id: Ie08216638c8a5bf7260fff8752a46aad06f53fcb