[Feature Request] Allow exporting KSP plugins

[ianb-pomelo]

Right now kt_jvm_library supports exporting compiler plugins but it does not support exporting KSP plugins. Java libraries do support exporting annotation processors, which lends itself to a nice pattern of having a target for a library that compiles the processor, a target with the plugin and a target that exports the plugin and the annotation it is associated with. However, since kt_jvm_library does not allow exporting KSP plugins, in order for the plugin to run when a class is annotated with an annotation, the user must know to also depend on the plugin, making it error prone.

Would it be possible to add support for exporting a KSP plugin so downstream users can depend on a single library that exports the dependency code and the plugin?