.gitlab-ci.yml: test algorithm

See vdj#386.
We use the same stages for browser and algorithm, I'm not sure this is a good practice.
See also #1491.
3 jobs for feature-a/ci in 15 minutes and 22 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test Unit
passed #18409
test_algo_unit

00:01:46

 
  Test Functional
passed #18410
test_algo_should

00:03:55

 
  Test Shouldvdj
passed #18411
test_algo_shouldvdj

00:09:39