revlog: migrate from PyEval_CallObject to PyObject_Call
The former was deprecated in 3.9.0.
Differential Revision: https://phab.mercurial-scm.org/D9791
fuzz: fix Makefile default PYTHON_CONFIG_FLAGS to be modern
This is actually what we already do on oss-fuzz, so it's more correct as tests
go.
Differential Revision: https://phab.mercurial-scm.org/D9790