Removed dependance on `rococo_parachain_runtime` for unrelated stuff (#1500)

* Clean misleading imports `rococo_parachain_runtime::{AccountId, AuraId}`

* Remove dependance on `rococo_parachain_runtime` for unrelated stuff

* fmt + rebase fix

* Addressing review comments

* Addressing review comments

* Fix for `purge_chain_works` works now with `rococo-local` and purge command needs to allow `rococo-native`