Migrate `dropdown-vue-component` in `app/assets/javascripts/environments/components/environment_item.vue`

Description

We use GlDropdown component in app/assets/javascripts/environments/components/environment_item.vue that should be migrated to GlCollapsibleListbox component as per Dropdowns > Vue > GlDropdown to GlCollapsibleLi... (&9371)

How to reproduce in Dev

Create an environment with a few deployments (you can use this config for reference)

Technical proposal

Since the app/assets/javascripts/environments/components/environment_item.vue component is already big enough, I'd suggest to move the dropdown to a separate component. As a part of this new component, we can prepare the items objects and a template to render the expected components for each actions.