Migrate boxWithJava tests to multi-file framework

compiler/testData/codegen/boxWithJava/collections/charSequence.kt

@@ -0,0 +1,68 @@
+// FILE: J.java
+
+import java.util.*;
+
+public class J {
+
+    public static class B extends A {
+        public int getLength() { return 456; }
+        public char get(int index) {
+            if (index == 1) return 'a';
+            return super.get(index);
+        }
+    }
+
+    public static String foo() {
+        B b = new B();
+        CharSequence cs = (CharSequence) b;
+
+        if (cs.length() != 456) return "fail 01";
+        if (b.length() != 456) return "fail 02";
+        if (b.getLength() != 456) return "fail 03";
+
+        if (cs.charAt(0) != 'z') return "fail 1";
+        if (b.get(0) != 'z') return "fail 2";
+
+        if (cs.charAt(1) != 'a') return "fail 3";
+        if (b.get(1) != 'a') return "fail 4";
+
+        return "OK";
+    }
+}
+
+// FILE: test.kt
+
+open class A : CharSequence {
+    override val length: Int = 123
+
+    override fun get(index: Int) = 'z';
+
+    override fun subSequence(start: Int, end: Int): CharSequence {
+        throw UnsupportedOperationException()
+    }
+}
+
+fun box(): String {
+    val b = J.B()
+    val a = A()
+
+    if (b[0] != 'z') return "fail 6"
+    if (a[0] != 'z') return "fail 7"
+    if (b[1] != 'a') return "fail 8"
+    if (a[0] != 'z') return "fail 9"
+
+    if (b.get(0) != 'z') return "fail 10"
+    if (a.get(0) != 'z') return "fail 11"
+    if (b.get(1) != 'a') return "fail 12"
+    if (a.get(1) != 'z') return "fail 13"
+
+    var cs: CharSequence = a
+    if (a.length != 123) return "fail 14"
+    if (cs.length != 123) return "fail 15"
+
+    cs = b
+    if (b.length != 456) return "fail 16"
+    if (b.length != 456) return "fail 17"
+
+    return J.foo();
+}