Add ci configuration for security prepare pipeline

What does this MR do and why?

Adds CI configuration for the security-prepare pipeline.

sequenceDiagram
    Parent Pipeline (preparation stage)-->>+security-prepare pipeline: Triggers downstream pipeline
    Note over Parent Pipeline (preparation stage): Not part of this issue
    security-prepare pipeline->>+security-prepare pipeline: Disable omnibus builds job
    security-prepare pipeline-->>+security-prepare pipeline: Check mirror status
    security-prepare pipeline-->>+security-prepare pipeline: Communicate security release
    security-prepare pipeline-->>+security-prepare pipeline: Check component pipeline status

This pipeline is not yet in use and at the moment it only executes a job to disable the omnibus nightly builds.

It also includes some code fixes discovered while testing.

Related to gitlab-com/gl-infra/delivery#19300 (closed)

Test

This branch was pushed to the ops instance for testing purposes

Job failed	Job succeeded
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Slack messages were posted to the #release_tools_test - Internal link only.

Author Check-list

• [-] Has documentation been updated?