Add benchmark for tempest. Part 2

Several new scenarios added in tempest benchmark:

* scenario for launching all tests

* scenario for launching all tests from given set(special set_name
validator was added for this scenario)

* scenario for launching all tests from given list of test names
(Also, test coverage for validator `tempest_tests_exists` was increased
for situations like in this scenario)

* scenario for launching all tests which match given regex expression

bp benchmark-scenarios-based-on-tempest

Change-Id: I3e715cb360dec3d5d8683a9001c4f2221b49d1ac
Merge "Add benchmark for tempest. Part 2"