Group more tests per YAML to reduce the number of envs created

[vloncar]

Description

As discussed during the dev meeting, the CI tests create a new environment for every test file, eventually exhausting the disk space of k8 runners. With this PR we reduce the number of parallel tests that run at the same time, thus reducing the number of environments created.

Type of change

• Other (Specify) - Testing infrastructure update

Tests

I arbitrarily set the number of test files that are run as one "unit" as 5. May need several iterations to fine-tune this.

Checklist

• I have read the guidelines for contributing.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• I have installed and run pre-commit on the files I edited or added.
• I have added tests that prove my fix is effective or that my feature works.