Refactor our Maven publication logic based on "gradle-maven-publish-plugin"

[ShreckYe]

"gradle-maven-publish-plugin" seems to provide mature support for Kotlin Multiplatform. Test their plugins, consider deprecating some of our plugins and basing on theirs. (And also check the code to see if we can contribute some of our code to their project)

[ShreckYe]

Also check if they have support for GitHub Actions and GitLab CI/CD.

[ShreckYe]

Also see https://kotlinlang.org/docs/gsoc-2025.html#maven-central-publishing-plugin-for-gradle-with-new-apis-medium-175-hrs.

[ShreckYe]

This is also now used in Kotlin Multiplatform's official tutorial.