[ROCm] Add skip-jaxlib-from-gcs to download action; run download for build_jaxlib=wheel
Adds skip-jaxlib-from-gcs input to download-jax-rocm-wheels so that
plugin/PJRT wheels can be fetched from S3 independently of jaxlib when
jaxlib is built from source. The download step in bazel_rocm.yml now
also runs for build_jaxlib=wheel, passing skip-jaxlib-from-gcs=1 to
skip the GCS jaxlib fetch while still downloading plugin/PJRT from S3.