Add a CI workflow that tests the init container

[kford-newrelic]

Description

As part of the GHA workflow that builds the init containers and as a CI flow for PRs opened that modify the init containers, each agent must create a test GHA workflow that validates that the init container(s) work.

This will likely be a collaboration with the kubernetes team (point of contact: Juan Jose Jaramillo) as we will want to validate it by using the k8s agent operator mutating webhook.

Python will create a GHA workflow for this first that other agents can copy modify for their own agent.

Acceptance Criteria

New GHA workflow that triggers when init container PRs are submitted.

Design Consideration/Limitations

N/A

Dependencies

N/A

Additional context

N/A

[workato-integration]

https://new-relic.atlassian.net/browse/NR-260160