JVM_IR: refactor ToArrayLowering and make matching more precise

* If `toArray` is inherited from Java, it may take an argument or
    return a value of a flexible type, which looks nullable in IR;
  * The returned array may also have `out` variance of the type
    argument;
  * `Array<T>` is not the same as `Array<Any?>` if `T` is neither `Any`
    nor `in Something`, so presence of `toArray(): Array<T>` does not
    mean we don't need to generate a new `toArray`.

compiler/testData/codegen/box/toArray/toArrayShouldBePublicWithJava.kt

@@ -1,4 +1,5 @@
 // TARGET_BACKEND: JVM
+// IGNORE_BACKEND_FIR: JVM_IR
 // WITH_RUNTIME
 // IGNORE_LIGHT_ANALYSIS