…repository

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Slight adoption by robstoll:
- still let AbstractKotlinCompile depend on task and not KotlinCompile
  as this was not good enough in the past (still resulted in warnings)

moreover:
- deactivate build-logic.publish-to-tmp-maven-repo and leave TODO
  for later

moreover:
- don't repeat plugins, treat it more like a tree without duplicates
- add slowTest/SuiteLogThreshold so that
  com.github.vlsi.gradle-extensions does not print all tests
- move dokka configure into re-usable extension function
- disable localRepoElements.outgoing as it causes that the build task
  suddenly depend on the publish task
- make sure DokkaMultiModuleTask executes cleanDokkaHtmlPartial of specs
  and verbs-internal project as we don't want it
- move dokka configuration to root-build convention plugin

and turn it into a single module
moreover:
- remove println debug statements
- remove unused dependency gradle-plugin in publishing
- move includeBuild for build-logic plugins into pluginManagement block

this way we also get rid of the UNUSED_VARIABLE warnings

most contributors won't have to do anything in those files
hence they should not be that prominently placed in the root dir IMO