Add tests for BluetoothPbapObexServer#onGet/onSetPath

Bug: 237548430
Test: atest BluetoothPbapObexServerTest
Ignore-AOSP-First: Merging into internal branches first
        in order to resolve merge conflict
Change-Id: Iaec622d8c110754d1d7c84fad8a8a056fa70b538
Merged-In: Iaec622d8c110754d1d7c84fad8a8a056fa70b538