Loose Detroy button in favor of close environment button

Continuation of https://gitlab.com/gitlab-org/gitlab-ce/issues/22191 If this issue gets implemented, this issue should be considered.

Currently its possible to "Destroy" 💥 an environment, without leaving a trace anywhere. This is sort of bad, as there should be a history

Loose the destroy button in favor of closing an environment. There is the distinction between a dynamic environment (aka review app, or environment created from gitlab-ci.yml file) and a manual environment (created with the "create environment" button).

Both should be able to be closed rather than destroyed.

cc: @markpundsack @ayufan