We are going to deprecate `WITH_RUNTIME` directive. The main reason
behind this change is that `WITH_STDLIB` directive better describes
its meaning, specifically it will add kotlin stdlib to test's classpath.
This commit:
- introduces tests explicating what is and isn't considered a
proper main method on the JVM backends.
- implements support for parameterless main methods on the JVM IR
backend
- See KT-34338 for more tests.