Implement manual deployment actions button

What does this MR do and why?

Describe in detail what your merge request does and why.

This MR adds manual actions button feature to the new version of environment details page.

Screenshots or screen recordings

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

How to set up and validate locally

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

1. Turn the feature toggle on in the rails console:

   Feature.enable(:environment_details_vue)

2. Navigate to Project -> Environments and click on one of the environments link.
3. If the environment has deployments, they will be listed there. If the environment doesn't have any deployments, you would need to create some. To simplify that you could clone this project: https://gitlab.com/andrei.zubov/pipelinestest and run a few deployment pipelines.
4. If you've used the example repo from the previous step, create some deployments to, for example, production environment (happens automatically on adding commits to master)
5. On production environment check that the button appeared with deploy-staging option.
6. Once clicked on deploy-staging action, check Staging environment details page for the new deployment to be created.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.