tests: garbage collect sqlite connections on Windows + Python 3.11

There seems to be a regression in Python 3.11, where the sqlite
connections are not deallocated, due to some internal changes in
Python 3.11, where they are now using LRU cache. They are not deallocated
until `gc.collect()` is not called.

See python/cpython#97641.
This affects only Windows, because when we try to remove the tempdir for
the exp run, the sqlite connection is open which prevents us from
deleting that folder.

Although this may happen in real scenario in `exp run`, I am only fixing
the tests by mocking `dvc.close()` and extending it by calling
`gc.collect()` after it. We could also mock `State.close()` but didnot
want to mock something that is not in dvc itself.

The `diskcache` uses threadlocal for connections, so they are expected
to be garbage collected, and therefore does not provide a good way to
close the connections. The only API it offers is `self.close()` and that
only closes main thread's connection. If we had access to connection,
an easier way would have been to explicitly call `conn.close()`.
But we don''t have such option at the moment.

Related: iterative#8404 (comment)
GHA Failure: https://github.com/iterative/dvc/actions/runs/3437324559/jobs/5731929385#step:5:57

Author: skshetry

tests/conftest.py

@@ -1,3 +1,4 @@
+import gc
 import json
 import os
 import sys
@@ -259,3 +260,19 @@ def mock_hydra_conf(mocker):
     # NOTE: using sentinel here so that any imports from `hydra.conf`
     # return a mock.
     sys.modules["hydra.conf"] = mocker.sentinel
+
+
+@pytest.fixture(autouse=True)
+def gc_collect_on_dvc_close_on_win_311(mocker):
+    if sys.version_info < (3, 11) and os.name != "nt":
+        return
+
+    from dvc.repo import Repo
+
+    close = Repo.close
+
+    def wrapped(repo):
+        close(repo)
+        gc.collect()
+
+    mocker.patch("dvc.repo.Repo.close", wrapped)