ci: Remove httpcore from requirements-testing.txt (#6622)

Remove the package from `requirements-testing.txt` and add it only as a dependency of the test suites that rely on it.
Add `dataclasses` as a dependency for all tests, to avoid unhandled `ImportError` exceptions that arose after moving the `httpcore` dependency.
This is part of environment cleanup before moving the remaining testing dependencies to a uv dependency group.

Author: alexander-alderman-webb

requirements-testing.txt

@@ -1,9 +1,9 @@
 pytest>=6.0.0
 pytest-cov
+dataclasses; python_version < "3.7"
 pytest-forked
 executing
 asttokens
 responses
-httpcore[http2]
 setuptools
 docker

scripts/populate_tox/config.py

@@ -108,8 +108,8 @@
                 "djangorestframework",
                 "pytest-django",
                 "Werkzeug",
+                "channels[daphne]",
             ],
-            ">=2.0": ["channels[daphne]"],
             ">=2.2,<3.1": ["six"],
             ">=3.0": ["pytest-asyncio"],
             "<3.3": [
@@ -433,7 +433,7 @@
         "deps": {
             "*": ["websockets<11.0", "aiohttp"],
             ">=22": ["sanic-testing"],
-            "py3.6": ["aiocontextvars==0.2.1", "dataclasses"],
+            "py3.6": ["aiocontextvars==0.2.1"],
             "py3.8": ["tracerite<1.1.2"],
         },
         "num_versions": 4,

scripts/populate_tox/tox.jinja

@@ -80,12 +80,12 @@ deps =
     # === Common ===
     py3.8-common: hypothesis
     common: brotli
+    common: httpcore[asyncio,http2]
     common: jsonschema
     common: pysocks
     common: pytest-asyncio
     common: pytest-timeout
     common: pytest_localserver
-    common: httpcore[asyncio]
     common: socksio
     common: werkzeug
     # See https://github.com/pytest-dev/pytest/issues/9621
@@ -105,6 +105,7 @@ deps =
     {py3.6,py3.7}-gevent: pytest<7.0.0
     {py3.8,py3.9,py3.10,py3.11,py3.12}-gevent: pytest
     gevent: brotli
+    gevent: httpcore[http2]
     gevent: jsonschema
     gevent: pysocks
     gevent: pytest-asyncio