Add a method to obtain an Executor from a TestLooper: the executor
executes on a new Handler on the test looper.
Bug: 73088768
Test: new unit test for executor
Change-Id: Ib0aa10011116a4d998f8d3a7434939338d9b516d
This permits sharing of test components used in connectivity tests.
Rename the MockLooper to TestLooper, reflecting that it is not a
true mock, but a manually controlled Looper for use in tests.
Bug: 28848133
Test: Tests consuming this library pass.
Change-Id: I57e11f9544c7bffdb02739ab2a921512b1b11874