Fix "Stop" button for deployment jobs fails in Merge Request widget UI

What does this MR do and why?

This MR adds stop action to a list of supported actions in the job_action_button. It can use the same mutation and error message as a play job, as it basically plays the job named "stop".

References

• #505591 (closed)

Screenshots or screen recordings

Before	After
Screen_Recording_2025-06-12_at_15.34.36	Screen_Recording_2025-06-12_at_15.34.57

How to set up and validate locally

1. Set up a Pipeline with a deploy_environment and stop_environment jobs as follows:

Click to expand

stages:
  - deploy
  - stop


deploy_environment:
    stage: deploy
    environment:
        name: production
        on_stop: stop_environment
    script:
        - exit 0
    rules:
    - if: $CI_MERGE_REQUEST_ID

stop_environment:
    stage: stop
    environment:
        name: production
        action: stop
    script:
        - exit 0
    when: manual
    rules:
    - if: $CI_MERGE_REQUEST_ID

2. Create a Merge Request based off the above branch, an MR pipeline should run.
3. Wait for the deploy_environment job to complete successfully, creating the production environment.
4. Click the stop_environment job button from the MR widget; verify the job runs and the environment is stopped.

MR acceptance checklist

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Related to #505591 (closed)