Add Westend & Rococo primitives (#808)

* Move chain primitives to a sub-folder.

* Update workspace members.

* Extract core parts of polkadot.

* cargo fmt --all

* Remove TODO.

* cargo fmt --all

* Fix crate names.

* Add to the latest API.

* cargo fmt --all

* Add nested lock files to ignore (generated during cargo fmt)

* Fix compilation.

* cargo fmt --all

* Fix ignore pattern.

* Address review comments.