Develocity Maven extension version should be configurable

Currently a version of the Develocity Maven extension is bundled with the Build Validation Scripts Maven distribution with no option to use a different version. This could be made configurable following a pattern similar to what is done in the Develocity GitLab Templates.

https://github.com/gradle/develocity-gitlab-templates/blob/f487b55b942fafd02c621c9a7a23c98c11ffcebd/develocity-maven.yml

This change would benefit users who are running an older version of Develocity than what is compatible with the bundled version but who want to use the latest version of the scripts. Additionally, it would reduce the size of the Maven distribution which benefits all Maven users and especially those who do not require the auto-injection functionality.

Start by reviewing the Develocity Maven Templates pattern linked in the issue and then locate how the Maven distribution bundles and injects the extension. Define the configurable version and verify that users can select another version while the distribution no longer bundles unnecessary extension contents.

Written by the indexing model from the issue text.