Maven publishing abandons staging repositories for existing package versions

Maven publishing is creating staging repositories even if the package version being released already exists in Maven. If there are a lot of such concurrent requests, this leads to Maven blocking publishing credentials since this impacts their cleanup process and also customers since it becomes a noisy neighbor issue.

We need to fix our [publishing script](https://github.com/cdklabs/publib/blob/main/bin/publib-maven) to check for existing version before starting the publishing process.

Related issue with Maven: https://issues.sonatype.org/browse/OSSRH-94655