Fix doctests

[cclauss]

DRAFT because there are 5 TODOs that I cannot fix because luarocks --local make fails on macOS.

• luarocks --local make fails on macOS and Windows #101

Move doctests from a module docstring to a class docstring to make running them much more reliable.

% python tests/test_lua.py # passes silently
% python -m doctest --verbose tests/test_lua.py # "27 passed."

Modify the last line of the docstring to change 3 to 33...

% python tests/test_lua.py # "26 passed and 1 failed."
% python -m doctest --verbose tests/test_lua.py # "26 passed and 1 failed."

Use # doctest: +ELLIPSIS directives only on the tests where they are needed instead of requiring the global command-line option.

Proven to pass on:

• GitHub Actions: Complete tests on macOS and Ubuntu #94

[cclauss]

>>> lua.execute("python = require 'python'")

Different undefined symbols on each version of Lua (lua_isstring vs, lua_rotate).

On lua5.1:

    RuntimeError: error executing code: error loading module 'python' from file './python.so':
    	./python.so: undefined symbol: lua_isstring

On lua5.3:

    RuntimeError: error executing code: error loading module 'python' from file './python.so':
    	./python.so: undefined symbol: lua_rotate

[cclauss]

Important

ALWAYS add the --lua-version option when running apt-installed luarocks!

All 8 tests pass at https://github.com/cclauss/lunatic-python/actions/runs/28926481993

[cclauss]

Closing in favor of #96.

• Add Github Actions workflow to run Python doctests #96