tests: migrate test-wireproto-serverreactor.py to our internal CBOR This leaves the only client of thirdparty.cbor as test-cbor.py, which appears to be testing the behavior of cborutil against cbor. We should figure out some appropriate test strings and drop thirdparty.cbor, but that's a mission for another day. Differential Revision: https://phab.mercurial-scm.org/D5522