[clean up] Remove old implementation of Environment folder page
Description
Now when the new folders page is online, we should clean up unused code.
Related files
a good starting point is the following files list:
app/assets/javascripts/environments/folder/environments_folder_view.vue
app/assets/javascripts/environments/folder/environments_folder_bundle.js
app/assets/javascripts/environments/mixins/environments_mixin.js
app/assets/javascripts/environments/components/container.vue
app/assets/javascripts/environments/folder/environments_folder_app.vue
We should not forget the related spec files and feature flags.
One of the next steps could be removing non-graphql related functionality from the environment item component.
Edited by Andrei Zubov