Add GHA upload workflow to publish packages

As RAPIDS has its own upload process that differs from conda-forge in
some particular ways, we just disable the conda-forge upload logic
altogether in the prior commits. Additional we enable GHA artifact
storage. This way preserve the artifacts from the conda-build jobs
somehow. There are just preserved on GHA instead of being uploaded to
Anaconda.org.

Here we add a new workflow to allow RAPIDS to handle uploads itself.
This way any upload strategy can be specified. Also if the upload
process changes in the future, this workflow can be updated to align
with that process. Lastly conda-smithy doesn't touch this custom
workflow file, so it will be unaltered by regular conda-smithy
re-rendering operations.

.github/workflows/upload.yml

@@ -11,14 +11,35 @@ jobs:
     runs-on: ubuntu-latest
     if: ${{ github.event.workflow_run.conclusion == 'success' }}
     steps:
-      - run: |
-          echo "Build passing"
-          exit 0
+      - uses: actions/download-artifact@v4
+
+      - uses: conda-incubator/setup-miniconda@v3
+        with:
+          activate-environment: base
+          conda-solver: libmamba
+          channels:
+            - conda-forge
+          channel-priority: strict
+          show-channel-urls: true
+          miniforge-version: latest
+
+      - name: Conda environment info
+        shell: bash -l {0}
+        run: |
+          conda info
+          conda config --show
+          conda list --show-channel-urls
+
+      - name: Upload packages to `rapidsai-nightly
+        shell: bash -l {0}
+        run: |
+          # Upload packages
+          ls
 
   on-failure:
     runs-on: ubuntu-latest
     if: ${{ github.event.workflow_run.conclusion == 'failure' }}
     steps:
       - run: |
-          echo "Build failing"
+          echo "Building the Conda packages failed"
           exit 1