test on 3.11 (#8196)

We don't have aiohttp support yet, due to which we have to install
without cythonized extension.

Similarly, there has been some changes in how dataclasses disallows some
mutable arguments to be set as a class property, due to which
`hydra.conf` fails to import in 3.11.

See https://github.com/python/cpython/pull/29867. For now, I have
patched the module and avoid importing as a pytest-plugin.

dvc-hdfs/pyarrow is not there yet, we'll usually see a release 2-3
months after official reelase.

dvc-hdfs is skipped in 3.11 in extras_requires. `--set-params` will
return a nice error message if hydra cannot be imported in 3.11. I
decided to only patch that in tests.

.github/workflows/tests.yaml

@@ -43,6 +43,9 @@ jobs:
       matrix:
         os: [ubuntu-20.04, windows-latest, macos-latest]
         pyv: ["3.8", "3.9", "3.10"]
+        include:
+        - {os: ubuntu-latest, pyv: "3.11-dev"}
+
     steps:
     - uses: actions/checkout@v3
       with:
@@ -68,6 +71,8 @@ jobs:
       run: |
         pip install --upgrade pip setuptools wheel
         pip install -e ".[dev]"
+      env:
+        AIOHTTP_NO_EXTENSIONS: ${{ matrix.pyv == '3.11-dev' && '1' }}
     - name: run tests
       timeout-minutes: 40
       run: >-