Sort regression tests by ascending time

[bhourahine]

Also, look for shorter tests for some of the slower ones.

[awvwgk]

An easy solution would be to add a cost descriptor to existing test, it could be easily generated in somewhat machine agnostic way by running the testsuite once sequentially and normalizing the cost roughly by the fastest test (with a lower limit where the test is considered instant). Generally, marking some more basic tests and splitting the testing in a multiple stages to avoid running expensive test when the basics fail would probably be more helpful (maybe similar like we are using the LONG_TEST marker now).