dillon1000/react

Update release scripts to support experimental releases (#17086)

* Download correct artifacts for release channel

Experimental builds should pull artifacts from the
`process_artifacts_experimental` job.

I think instead of two separate CI workflows, a better approach might
be to build stable artifacts to the `build` directory and the
experimental artifacts to a `build_experimental` directory, and
generate both within the same workflow. This would take some work since
lots of things assume the output directory is `build`, but something
to consider in the future.

* Prevent experimental promotion to stable

Adds a check to the `prepare-stable` script to prevent experimental
builds from being published using stable semver versions.