New J2K: Split old j2k and new j2k tests

j2k/testData/fileOrElement/mutableCollections/FunctionReturnValue.new.kt

@@ -1,13 +0,0 @@
-import java.util.*
-
-internal class A {
-    fun createCollection(): MutableCollection<String> {
-        return ArrayList()
-    }
-
-    fun foo(): Collection<String> {
-        val collection = createCollection()
-        collection.add("a")
-        return collection
-    }
-}

j2k/testData/fileOrElement/mutableCollections/FunctionReturnValue2.new.kt

@@ -1,21 +0,0 @@
-import java.util.*
-
-internal class A {
-    private val collection: MutableCollection<String>
-
-    init {
-        collection = createCollection()
-    }
-
-    fun createCollection(): MutableCollection<String> {
-        return ArrayList()
-    }
-
-    fun foo() {
-        collection.add("1")
-    }
-
-    fun getCollection(): Collection<String> {
-        return collection
-    }
-}

j2k/testData/fileOrElement/mutableCollections/Iterator2.new.kt

@@ -1,11 +0,0 @@
-class TestMutableCollection {
-    val list: MutableList<String> = ArrayList()
-
-    fun test() {
-        val it = list.iterator()
-        while (it.hasNext()) {
-            val s = it.next()
-            if (s == "") it.remove()
-        }
-    }
-}