core/ci: fix windows-specific issues

- use portable separators
- paths should be prepended with r' (so backwards slash isn't treated as escaping)
- sqlite connections should be closed (otherwise windows fails to remove the underlying db file)
- workaround for emojis via PYTHONUTF8=1 test for now
- make ZipPath portable
- properly use tox python environment everywhere

  this was causing issues on Windows
  e.g.
      WARNING: test command found but not installed in testenv
        cmd: C:\hostedtoolcache\windows\Python\3.9.12\x64\python3.EXE

tests/cli.py

@@ -1,4 +1,14 @@
+import os
 from subprocess import check_call
 
 def test_lists_modules() -> None:
-    check_call(['hpi', 'modules'])
+    # hack PYTHONUTF8 for windows
+    # see  https://github.com/karlicoss/promnesia/issues/274
+    # https://memex.zulipchat.com/#narrow/stream/279600-promnesia/topic/indexing.3A.20utf8.28emoji.29.20filenames.20in.20Windows
+    # necessary for this test cause emooji is causing trouble
+    # TODO need to fix it properly
+    env = {
+        **os.environ,
+        'PYTHONUTF8': '1',
+    }
+    check_call(['hpi', 'modules'], env=env)