Add a separate test configurations for JDK 21 dependent test

After it's released, there would be no need in them, but right now
they are unavailable through the toolchain, so we can't require it.
See KT-58765 for tracking

But there should be a dedicated Build configuration with JDK_21_0 env
properly set.

^KT-58716 Fixed

compiler/tests-java8/tests/org/jetbrains/kotlin/serialization/builtins/AdditionalBuiltInsMembersSignatureListsTest.kt

@@ -75,6 +75,7 @@ class AdditionalBuiltInsMembersSignatureListsTest : KotlinTestWithEnvironment()
         }
     }
 
+    // TODO: Get rid of it once JDK 21 is released (KT-58765 for tracking)
     private val LATE_JDK_SIGNATURES = mapOf(
         "java/util/List" to setOf(
             // From JDK 21