Extend pipeline execution policy documentation to describe `inject_policy_ci`

documentation

Why are we doing this work

We're adding a new pipeline_config_strategy for pipeline execution policies. We should update documentation to explain:

  • how it works
  • why it's useful
  • explain how the stages definition works
  • explain which stage definition could lead to pipeline failures (cyclic dependencies)
  • mark inject_ci as deprecated

Relevant links

Verification steps

Edited by Martin Cavoj