Monorepo independent flow: Include build number in release version

It is possible to create multiple release branches on the same day. To do this, the release version must be unique. We can do this by including a build number in the release version. Right now the release version is formatted as `YYYY.MM.DD`. We want to change this to `YYYYMMDD.BUILD_NUMBER.0`, and we want to increment the `BUILD_NUMBER` for every fresh run of this tool.