Add sources and javadoc jars to publication, Fix staging directory

[haydenbaker]

Description of changes:

• Staging directory was incorrectly set
  • ex: the directories getting created were named /property(org.gradle.api.file.Directory, fixed(class org.gradle.api.internal.file.DefaultFilePropertyFactory$FixedDirectory, / under each module's build dir
    • specifically, DirectoryProperty being interpolated, which doesn't have a toString method
  • This may have still worked because the dirs still get created and populated, but it's still wrong
  • The correct path is build/staging, and all publications should be put there
• Javadoc and Sources jars were not being created in the publications
• framework-errors package had some ordering and duplication issues, workarounds added

Testing:

• gradle clean build publish
• set up dummy signing secrets with JReleaser, run gradle jreleaserRelease
• inspect trace log, should fail (no nexus credentials)
  • verify POM checker passes
  • verify artifacts are signed

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