Upgrading build scripts

• Part of [ci] Improve GH Actions scripts #2967

Tasks:

• ✔️ Bump dokka from 1.4.10.2 to 1.4.30
  Remove workaround for Use maven directly to download additional dependencies Kotlin/dokka#1644
• ✔️ using the new scripts
• ✔️ tested locally with docker: push, pull request
• ✔️ testing on github actions with this PR (only pull request)
• ✔️ testing locally a release build
• ✔️ doc: https://github.com/sonatype/nexus-maven-plugins/tree/master/staging/maven-plugin (this is added in pmd/build-tools)
• ✔️ doc: Move remote ssh debugging to build-tools
• ✔️ doc: infrastructure
  • github
  • sourceforge
  • domains and homepage: pmd-code.org (netcup)
  • maven-central (ossrh)
• ✔️ doc: what happens during build/release on github actions? where are the artifacts supposed to be deployed to, where is the documentation supposed to be upated, ... what are the artifacts? (binaries, jars, doc.zip, baseline for regression tester)
• ✔️ release build-tools
• ✔️ prepare pull request for pmd7 -> [ci] Upgrade build scripts (pmd7 merge) #3233

Improvements:

• ✔️ move -DautoReleaseAfterClose=true on command line instead in pom.xml - to allow overriding when needed
• ✔️ automatically create a news blogpost on sourceforge for the release (like release notes)
  • possible via "pmd_ci_sourceforge_createDraftBlogPost" and "pmd_ci_sourceforge_publishBlogPost"
• ✔️ New workflow for synchronizing git repo github->sourceforge: "git-repo-sync"

Notes / Ideas for later:

• it seems, that the dokka plugin doesn't run with java16. Also, if I remember correctly, nexus-staging-maven-plugin fails with java16, too. That's not a problem yet, since we still build with java11.
  workaround: MAVEN_OPTS="--illegal-access=permit" ./mvnw clean verify
  See also https://youtrack.jetbrains.com/issue/KT-44624
• dry-run: especially for testing the release build, a "dry-run-mode" would be useful -> Support dry-run mode build-tools#19
• better support for debugging: currently via PMD_CI_DEBUG=true, but github actions also supports this: https://docs.github.com/en/actions/managing-workflow-runs/enabling-debug-logging -> Better support for debugging build-tools#20