CITest: add start/stop timestamps to CI tests
Add start and finish timestamps to CI tests. These are used by NICOS for bookkeeping and monitoring (ATLINFR-4360).
Example:
[CITest][DuplicateClass] start time: Mon Jan 31 15:13:34 CET 2022 (1643638414.275365951)
...
[CITest][DuplicateClass] end time: Mon Jan 31 15:13:36 CET 2022 (1643638416.432128454)
cc @aundrus