Move default implementation of TargetPlatform.platformName to leaf classes

Otherwise, we have a static initialization loop, leading to null-leaks

Removing default interface method indeed disconnects the loop, as per JVM
Specification, "5.5 Initialization".

See KT-33245 for detailed explanations

^KT-33245 Fixed

compiler/frontend.java/src/org/jetbrains/kotlin/platform/jvm/JvmPlatform.kt

@@ -45,7 +45,10 @@ object JvmPlatforms {
     )
     object CompatJvmPlatform : TargetPlatform(setOf(UNSPECIFIED_SIMPLE_JVM_PLATFORM)),
         // Needed for backward compatibility, because old code uses INSTANCEOF checks instead of calling extensions
-        org.jetbrains.kotlin.resolve.jvm.platform.JvmPlatform {}
+        org.jetbrains.kotlin.resolve.jvm.platform.JvmPlatform {
+        override val platformName: String
+            get() = "JVM"
+    }
 }
 
 class JdkPlatform(val targetVersion: JvmTarget) : JvmPlatform() {

compiler/frontend.java/src/org/jetbrains/kotlin/resolve/jvm/platform/JvmPlatform.kt

@@ -16,10 +16,6 @@ import org.jetbrains.kotlin.resolve.TargetPlatform
     level = DeprecationLevel.ERROR
 )
 interface JvmPlatform : TargetPlatform {
-    @JvmDefault
-    override val platformName: String
-        get() = "JVM"
-
     companion object {
         @JvmField
         val INSTANCE: JvmPlatform = JvmPlatforms.CompatJvmPlatform