Create an RC Tag

Create the tag only after the release branch has been created.

Determine the version

Require the user to provide the stable release version in either <major>.<minor> or <major>.<minor>.<patch> form. Treat a two-component version as <major>.<minor>.0. Do not infer the version from Cargo.toml or a branch name, and do not edit Cargo.toml while cutting the tag. Normalize the supplied version into RELEASE_BASE_VERSION: