chore(workload): disable access to unreturned data attributes in data method

[ly5156]

Summary

Fixes #13001

Occurred changes and/or fixed issues

The data method is expected to return a plain JavaScript object, which will be made reactive by Vue. Accessing or modifying unreturned data attributes in the data method may result in undesired issues

ref: https://vuejs.org/api/options-state.html#data

Technical notes summary

1. When the component is initialized, the method call to select the first container is placed in the created lifecycle hooks.
2. watch the active container changes and update fvFormRuleSets, in order to display the image form status in real time.

Areas or cases that should be tested

1. should manual test that the form error prompts for the container are correct when creating or editing a workload
   ref: The general tab section missing error message on the Create or Edit workload page #13001

Areas which could experience regressions

Screenshot/Video

Checklist

• The PR is linked to an issue and the linked issue has a Milestone, or no issue is needed
• The PR has a Milestone
• The PR template has been filled out
• The PR has been self reviewed
• The PR has a reviewer assigned
• The PR has automated tests or clear instructions for manual tests and the linked issue has appropriate QA labels, or tests are not needed
• The PR has reviewed with UX and tested in light and dark mode, or there are no UX changes

[rak-phillip]

@ly5156 Thanks for this change - it looks good and functions as described. I made sure to assign a proper milestone to this PR and the associated issue.

Can you make sure that the rest of the checklist is completed? We will not pass CI gates without this.