Fuse hspec and tasty drivers into one
This commit fuses the two drivers into a single one.
With some appropriate usage of beforeAllWith, even running all the
specs in parallel seems to be yielding the expected results.
Locally this works, but we have to keep an eye if we get any flaky WS-related tests, as I have spotted a few once fixing the testsuite.
However, we have seen the WS tests acting in a flaky way recently as well, so these changes might be simply exposing a problem which was already there.