Add JSON type definitions for Rococo<>Wococo bridge (#977)

* Add Rococo and Wococo types to common.json

* Add Rococo/Wococo specific JSON definitions

* Add Rococo/Wococo support to types build script

* Get updated type definitions from build script

* Split bridge-pair specific definitions from `common.json`

* Get new type definitions from build script

* Make Wococo types reference Rococo types

Types in Wococo should always match those of Rococo since they use
the same runtime.

* Use default Header type for Rococo and Wococo headers

* Build new Rococo and Wococo type definitions