Clean up old pipeline runs in jobs

[ricklamers]

Is your feature request related to a problem? Please describe.
When running a pipeline as part of a job, the job can create many pipeline runs when e.g. on a short cron schedule (run every 5 minutes). Each run has its own "checkout" of the project files. This can fill the disk pretty rapidly in some cases (large project files, e.g. node_modules/ in some cases).

Describe the solution you'd like
Introduce an option to retain only the last X number of pipeline runs. This automatically frees up space and allows cron jobs to run for longer durations more reliably.

Credits to Serhii Ostapchuk for bringing up the problem & idea.