Add `legacyShrinking` to PropertyCheckConfiguration

Sadly, ScalaCheck allows [legacyShrinking](https://javadoc.io/static/org.scalacheck/scalacheck_2.11/1.14.1/index.html#org.scalacheck.Test$$Parameters@useLegacyShrinking:Boolean) by default. In some situations this results in in useless, misleading and counter-productive test failure meassages. Please, add `legacyShrinking` to `PropertyCheckConfiguration`.