[Test] Properly merge box against java testdata into codegen/box

Previous commit about it was 3199ce03 and it was completely wrong

compiler/testData/codegen/box/oldLanguageVersions/ieee754/explicitEqualsCallNull.kt

@@ -0,0 +1,34 @@
+// DONT_TARGET_EXACT_BACKEND: JS JS_IR JS_IR_ES6 WASM NATIVE
+// !LANGUAGE: -ThrowNpeOnExplicitEqualsForBoxedNull
+// IGNORE_BACKEND: JVM_IR
+// ^ ThrowNpeOnExplicitEqualsForBoxedNull is introduced in 1.2.
+// MODULE: lib
+// FILE: JavaClass.java
+
+public class JavaClass {
+
+    public Double minus0(){
+        return -0.0;
+    }
+
+    public Double plus0(){
+        return 0.0;
+    }
+
+    public Double null0(){
+        return null;
+    }
+
+}
+
+
+// MODULE: main(lib)
+// FILE: b.kt
+
+fun box(): String {
+    val jClass = JavaClass()
+
+    if (jClass.null0().equals(jClass.plus0())) return "fail 6"
+    if (jClass.minus0().equals(jClass.null0())) return "fail 7"
+    return "OK"
+}