It is required to run tests authored with kotlin-test, so it seems
convenient to have it as a runtime dependency of kotlin-test-junit5
variant.
Depend on the version 5.6.0, which is approx. one year old.
Can be upgraded in the consumer project if necessary.
Also upgrade junit-jupiter-api dependency to 5.6.0, so that users could
use more recent JUnit functionality in JVM tests,
but continue compiling the artifact against 5.0.0 to leave a
possibility to downgrade JUnit platform dependency if needed.
KT-45107
Ilya Gorbunov
284e6f5bb3