general: make time.tz.via_location user config lazy, move tests to my.tests package

also gets rid of the problematic reset_modules thingie

my/tests/conftest.py

@@ -1,8 +1,10 @@
 import pytest
 
+
 # I guess makes sense by default
 @pytest.fixture(autouse=True)
 def without_cachew():
     from my.core.cachew import disabled_cachew
+
     with disabled_cachew():
         yield