Fix pkg-helpers conda env: explicitly install pip (pytorch#8035)

Conda 25.x (now resolved as miniconda `latest`, after pytorch#7753 upgraded
conda to 25.3.0) no longer installs `pip` by default when only
`python=X.Y` is requested in `conda create`, which breaks the
`pytorch_pkg_helpers` step in `setup-binary-builds/action.yml`, which
immediately calls `python -m pip install ...` against the new env and
fails with `No module named pip` (e.g. observed in torchcomms wheel
builds).
Fix: add `pip` explicitly to the `conda create` invocation so the env is
usable regardless of conda's default-package behavior.

Author: malfet

.github/actions/setup-binary-builds/action.yml

@@ -113,7 +113,7 @@ runs:
           conda create \
             --yes --quiet \
             --prefix "${CONDA_ENV}" \
-            "python=3.9"
+            "python=3.9" pip
           CONDA_ENV="${CONDA_ENV}"
           CONDA_RUN="conda run --no-capture-output -p ${CONDA_ENV}"
           ${CONDA_RUN} python -m pip install ${GITHUB_WORKSPACE}/test-infra/tools/pkg-helpers