[KSP2] Generated resources are not added to KotlinCompilation inputs

[ZacSweers]

Between K2 Beta1 and Beta3, this appears to have regressed and generated resources are no longer added as inputs to the Kotlin compilation. Sorry realizing this is actually just specific to KSP2.

Repro: slackhq/EitherNet#72

In this project, there is a test called EitherNetControllersTest that exercises a service loader code path. This service loader is generated by auto-service-ksp, and the specific impl loaded in this class is SlackEndpointValidator.

I do see the service file generated, but I do not see it marked as a source dir or visible at runtime, resulting in the current test failure on that PR.

[ting-yuan]

Turns out that this is caused by a bug in KSDeclaration.packageName which incorrectly returned an empty string for classes in libraries. In this case, the entire com.slack.eithernet.test.ApiValidator is treated as class name with an empty package name and therefore the com$slack$eithernet$test$ApiValidator in the screenshot. The package name issue is already fixed in #1724.

Verified with 2.0.0-Beta4-1.0.18-SNAPSHOT.