The glorious return back to core

[andreaTP]

"Everything must change for everything to remain the same"
Il Gattopardo

TODO:
before this PR gets merged the release process should be tweaked and we should verify that all the artifacts are published as expected.

[debasishg]

@andreaTP One general observation. Lots of changes (in fact most of them) comes from scalafmt version and rule changes. It would have been easier to check if these formatting changes were in a separate PR.

[debasishg]

Almost all of the PR is refactoring code from tools to core and changes in formatting through the new rules and version of scalafmt. LGTM

[andreaTP]

@debasishg you are right but it would have taken me double the time to keep scalafmt in one commit, unfortunately 😢 sorry.

Minor caveats:

• cannot get javaformatter to reliably work cross Java 8 - 11 have had to disable it
• bumped the entire codebase to ScalaTest 3.2 -> this bump is possibly going to break user's tests and they are forced to bump
• we would need to re-enforce back some scalacOptions.