ci: Migrate aws creds to managed IAM

Migrates our current credentials for AWS to managed IAM users so that we
can scale our user set without having to be active in doing it.

Signed-off-by: Eli Uriegas <eliuriegasfb.com>

Pull Request resolved: pytorch#73516

.github/templates/upload.yml.j2

@@ -71,8 +71,8 @@
           PKG_DIR: "${{ runner.temp }}/artifacts"
           UPLOAD_SUBFOLDER: "${{ env.DESIRED_CUDA }}"
           # When running these on pull_request events these should be blank
-          AWS_ACCESS_KEY_ID: ${{ secrets.AWS_PYTORCH_ACCESS_KEY_ID }}
-          AWS_SECRET_ACCESS_KEY: ${{ secrets.AWS_PYTORCH_SECRET_KEY }}
+          AWS_ACCESS_KEY_ID: ${{ secrets.AWS_PYTORCH_UPLOADER_ACCESS_KEY_ID }}
+          AWS_SECRET_ACCESS_KEY: ${{ secrets.AWS_PYTORCH_UPLOADER_SECRET_ACCESS_KEY }}
           ANACONDA_API_TOKEN: ${{ secrets.CONDA_PYTORCHBOT_TOKEN }}
         run: |
           docker run --rm -i \