Suggestion for Grails 5+: supersede/deprecate some of the grails-gradle-plugin features with Gradle native implementation

I believe some of the grails-gradle-plugin features can now be used with Gradle natively. To be future proof and reduce maintenance I think it would be nice to rewrite some of the current grails-gradle-plugin implementation with the Gradle native variants.

Some examples:
- remove pathingJar as this is now implemented in Gradle itself
- I think the exploded classpath (for multi-module projects) could be replaced by Gradle's variant attributes
- with variant attributes the Grails specific plugin-dependencies block could surely be dropped (use the standard Gradle dependency block)

Start by examining the grails-gradle-plugin implementation for pathingJar, the exploded classpath, and the Grails-specific plugin-dependencies block. Compare each feature with Gradle's native implementation and variant attributes; done means an agreed, tested plan to supersede or deprecate the redundant features.

Written by the indexing model from the issue text.