chore: simplify pom.xml

Remove dead/obsolete plugins and config:
- maven-release-plugin (replaced by GitHub Actions)
- cobertura-maven-plugin (abandoned, incompatible with modern Java)
- coveralls-maven-plugin (abandoned, not used in CI)
- formatter-maven-plugin (replaced by fmt-maven-plugin)
- maven-scm-publish-plugin (replaced by GitHub Actions Pages deploy)
- maven-site-plugin (no longer running mvn site)
- Entire <reporting> section (broken/stale plugins)
- Java 8 profile (minimum is now Java 11)
- Java 9+ profile (inlined maven.compiler.release into properties)
- distributionManagement/snapshotRepository (unused with central-publishing-maven-plugin)
- Duplicate central-publishing-maven-plugin version

Author: bramp