Extending PrivateLoadZone with image and env vars

[yorugac]

Feature Description

/loadtests/v4/test_runs(<id>) endpoint has been extended with a new data field:

• k8s_load_zones_config.environment a dict of key-value pairs

And PLZ registration endpoint now accepts config.load_runner_image with a string of public Docker k6-based image.

Suggested Solution (optional)

Update PLZ CRD to accept image configuration. Extend GCk6 API calls correspondingly.

• image in k6 pods must be set to the one configured, when available
• env vars are supposed to be propagated to all k6 pods

Already existing or connected issues / PRs (optional)

No response