src: use ==/!= to compare str, bytes, and int literals

Add a more flake8 tests

* F63 tests are usually about the confusion between identity and equality in Python.
* F7 tests logic errors and syntax errors in type hints

meta: stabalize CI configuration

src: allow local pymod_do_main modules

testlib: allow passing list of tests to gyptest.py

src: more tree-refactoring

move