minimal changes to compile a 2.13.x compatible version

[ahepburn-sumologic]

note - this requires java8 to build locally due to sun.misc.unsafe usage (unchanged in later kamon)

• intention is to publish this to sumo repos
• this PR is really just illustrative, latest 1.1. maintenance is 1.1.6, since we're on 1.1.2 everywhere this targets only including what is in 1.1.2 but published for 2.13
• Kamon 2.* (the first version stably cross-compiled for Scala 2.13) has significant changes, whereas the changes to compile 1.1.x are actually minimal
• official 2.12 artifacts exist, so no attempt was made at preserving 2.12 here: all we want is a published artifact
• we should update kamon... but that work is much larger in scope than resolving the lack of a 2.13 version of kamon-core