EPIC: Testing environment checks

TKG should do general testing env checks before and/or after running the test. Below are something we could take a look to see if we should implement:

- [x] diskspace (fail if we do not have enough diskspace)

- [x] memory (fail if we do not have enough memory)

- [ ] core (fail if there is core generated after a test run regardless of the test result)

- [ ] list existing running processes before and after the test (fail if there is any dangling process?), this includes docker images leftover from aborted runs, those are not expected to be present and should get pruned

- [ ] a flag to enable/disable this test environment health checks

Start by reviewing the existing diskspace and memory checks, since the issue marks both as complete. Then assess the remaining proposals—core-file detection, process and Docker cleanup checks, and a flag to enable or disable health checks—and clarify their scope and acceptance criteria. Done should be defined for each selected check before implementation begins.

Written by the indexing model from the issue text.