Return CancellationSignal when opening UWB session

Returns a CancellationSignal instead of an AutoCloseable when calling
UwbManager#openRangingSession per API feedback.

Bug: 180396069
Test: atest UwbManagerTests CtsUwbTestCases
Change-Id: I74482c56d1a3686b570c90e7d3c11e45ec2f0adc
Merged-In: I74482c56d1a3686b570c90e7d3c11e45ec2f0adc