Use Typelevel scalac options

[steinybot]

I was working on #390 which adds a few different projects for the code gen and configuring the different options for the different scala versions was a pain. This makes it a fair bit easier and removes some of the existing workarounds.

I didn't go as far as adding https://github.com/typelevel/sbt-tpolecat although that would be my preference.

I "fixed" (ignored) a few warnings which possibly started showing up as I didn't remove as many warnings for the projects with Scala 2.12.

There are still 2 left:

[warn] -- Warning: /Users/jason/src/kyo2/kyo-stats-registry/js/src/main/scala/kyo/stats/internal/UnsafeHistogram.scala:3:22
[warn] 3 |class UnsafeHistogram(numberOfSignificantValueDigits: Int, highestToLowestValueRatio: Long) {
[warn]   |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[warn]   |                      unused explicit parameter
[warn] -- Warning: /Users/jason/src/kyo2/kyo-stats-registry/js/src/main/scala/kyo/stats/internal/UnsafeHistogram.scala:3:59
[warn] 3 |class UnsafeHistogram(numberOfSignificantValueDigits: Int, highestToLowestValueRatio: Long) {
[warn]   |                                                           ^^^^^^^^^^^^^^^^^^^^^^^^^
[warn]   |                                                 unused explicit parameter

[steinybot]

I couldn't use the @unused annotation because it isn't available in Scala 2.12. You are supposed to be able to annotate with : Unit to avoid discarded non-unit value warnings but I have very little success using that approach. Perhaps UnsafeGuage should have a void method or there should be another gauge method that returns Unit?

[fwbrasil]

Metrics are held via weak references in kyo-stats-registry so we need the class field holding the gauge reference to avoid it getting garbage collected. Maybe we could move kyo.discard to kyo-scheduler?

[steinybot]

I moved discard to kyo-scheduler but it is using Scala 3 top level function definitions and so isn't going to work. I'll have to come up with something else.

[steinybot]

Ok scratch that. You already removed the -Wunused:all option so this is now a non-issue.

[steinybot]

Scrapping this in favor of #485