Support development in Py3.11

[fjarri]

While pons itself works fine in 3.11, the tests cannot be run since the eth-tester[pyevm] dependency installs a deprecated pysha3 which evidently cannot be compiled in 3.11:

      In file included from Modules/_sha3/sha3module.c:20:
      Modules/_sha3/backport.inc:78:10: fatal error: 'pystrhex.h' file not found

(MacOS 12.6)

Edit: opened ethereum/eth-tester#248