Gy 50k fixes

Closes #91 (closed)

Adds in a tag for k6 tests to use newly setup autoscaling GitLab Runner on gitlab-qa-resources project that spawns machines with increases specs (custom type - 4 cpu 8gb memory) required for running k6 at bigger scales.

This moves all k6 test to use the same runners for consistency (autoscaling means minimal costs) as well as avoiding some other shared runners that are "highcpu" which also means low memory that additionally cause k6 to fail.