[FE] Allow to add/remove snippet files in the edit view

After adding the new files type in the snippet create/update mutations in #217795 (closed) and #217799 (closed) we need to update VUE to use this new type.

One important thing about this new type, is that in every update operation, each snippet blob has to have a previous_path that will store the path that has in the repository. The field file_name will be the new path. Most of the times, these paths will be the same, but it won't if the user wants to, for example, rename the file.

We need to remove the reference to content and file_name from the request to the snippet mutations.

Besides, we need to use the action definition implemented in #218516 (closed) (it's the same one the web IDE uses).

After adding, users should also be able to remove snippets again

• Make sure Editor Lite can run multiple instances on the same page
• Allow to dynamically add Files to the mutation
• Allow to remove Snippets from the list

Availability and Testing

Please include a SET counterpart in MR review