Improve build times for library code

[cmelchior]

In order to bring down build times on CI we need to add support for building and testing the library in parallel. Some first steps seems to be:

• [ ] Enable https://kotlinlang.org/docs/multiplatform-publish-lib.html#avoid-duplicate-publications, i.e. it should be possible to configure our packages to only build and publish artifacts for a specific platform. This will also increase developer speed as we can restrict the number of platforms being built.

• [ ] There seem to be problems with our JVM libraries not being correctly invalidated, which means that changes to native code often require cleaning the workspace. We need to investigate the Gradle Task graph to figure this out. Probably we are misconfiguring input/outputs somewhere.