Add action to pipeline execution policy

What does this MR do and why?

Add action to pipeline execution policy

• move code action to pipeline execution folder
• hide remove button
• update tests

What does this MR not do and why?

• does not hook up any real functionality yet. Saving all that complicated logic for a future MR
• does not implement any updated design changes from #452328[step2-new-plolicy-editor.png]; saving that for a future MR, so this doesn't need a design review

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Scenario	ff off	ff on
Scan execution		ff_on
Pipeline execution	N/A

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Upload a GitLab Ultimate license
2. Enable feature flag

echo "Feature.enable(:pipeline_execution_policy_type)" | rails c

3. Navigate to http://gdk.test:3443/gitlab-org/gitlab-test/-/security/policies/new?type=pipeline_execution_policy

Related to #454284 (closed)