Log images used by job

What does this MR do?

Log images used by job

Why was this MR needed?

Depending on the used executor, a job may be configured with an image and/or service images to use.

In some cases it will be very useful to the Runner owner to track what images are used: for copliance reasons, for statistics, to know what to pre-provision in the job environment or to check whether there are images in use that may break the jobs once a specific configuration change to the runner is applied.

This commit adds logging of these images.

Depending on the specific configuration of Runner and most importantly - the job - this change may significantly increase the number of log output produced by Runner. Therefor, for now, it's hidden behind a feature flag that is disabled by default.

What's the best way to test this MR?

What are the relevant issue numbers?