[entity:delete] Allow deleting all entities of a type.

[cburschka-pwc]

Uninstalling a module via the console frequently fails because the module has created content entities, which need to be deleted:

 [ERROR] The following reasons prevent the modules from being uninstalled:
    There is content for the entity type: @entity_type. <a href=":url">Remove @entity_type_plural</a>.  

It would be great if this deletion could be performed via the console as well. Currently entity:delete only deletes a single entity.

Proposed solutions:

1. Add a new command, entity:delete:all <type>.
2. Add an optional argument so that entity:delete <type> --all deletes all entities of the given type.

[cburschka-pwc]

(Merged)