Remove user input from the build release container

When building a release for checking reproducible builds, we currently
require that users manually select the project name and enter the
release candidate label. This can make it difficult to script and can
lead to errors when entering the information. This user input is really
just relic of when we required a lot more information. The current
script only needs couple of pieces of information (project name and
optional release label), so manual input isn't the best way to get that
information anymore.

This changes the script so the project name and optional release label
must be provided as arguments to the script, removing all user input.
Validation is added to ensure the project name is one of the expected
projects and the pre-release label (if provided) is a valid release
candidate label.