They are beginning to block the pipeline for too long.

[ci skip]

* Reduce pytest xml log size
* store artifact to debug
* Fix test result path

* Do tests with pytest to run them in parallel

* attempt to handle merge commits better for PR test path

Similar to how we solved this for travis

* Clean up imports

* don't run valgrind if not specified slow_test

* Fix functest after initializer rename

* upload tests results as junit

* Upload test-common files since #200 got merged

* Catch test results upload failure

Also specifies an order on the PQCLEAN builds to limit fruitless
testing.

It seems to have worked in CircleCI without this, though;
it is unclear to me why.

use randombytes in functest

Got dropped by the rebase

Work around missing clang-tidy on Travis

Also check if valgrind is available

Build on circleci, should be much faster.