Provide a plugin ID that complies with modern Gradle conventions

[JakeWharton]

Per https://docs.gradle.org/current/userguide/custom_plugins.html#sec:creating_a_plugin_id

Plugin ids are fully qualified in a manner similar to Java packages (i.e. a reverse domain name). This helps to avoid collisions and provides a way to group plugins with similar ownership.

Please provide a plugin ID in this form. The old one can remain as an alias or undergo a deprecation cycle.

I would assume given the Maven coordinates that it should be org.jetbrains.kotlinx.binary-compatibility-validator.