De-incubate Javadoc/Sources publishing and compileOnlyApi

[jjohannes]

Summary

org.gradle.api.plugins.FeatureSpec.withJavadocJar()
org.gradle.api.plugins.FeatureSpec.withSourcesJar()
org.gradle.api.plugins.JavaPluginExtension.withJavadocJar()
org.gradle.api.plugins.JavaPluginExtension.withSourcesJar()
org.gradle.api.tasks.SourceSet.getCompileOnlyApiConfigurationName
org.gradle.api.tasks.SourceSet.getJavadocElementsConfigurationName()
org.gradle.api.tasks.SourceSet.getJavadocJarTaskName()
org.gradle.api.tasks.SourceSet.getJavadocTaskName()
org.gradle.api.tasks.SourceSet.getSourcesElementsConfigurationName()
org.gradle.api.tasks.SourceSet.getSourcesJarTaskName()

Checklist

• Validate whether we should de-incubate the API in the 7.0 release.
  • If the removal is not possible, create a follow-up issue and link it in the overview spreadsheet
• Update release notes (add API to promoted features)
• Check User Manual (it might mention that the API is still incubating)
  • Think about updating snippets and samples to use this API
• [ ] Deprecate existing API that is replaced by the new one
• Check Incubation Report on TeamCity (example)
• Mark the story as done in the overview spreadsheet.