IR: don't produce fake overrides for static and private declarations

Note that only irrelevantStaticProperty.kt failed before this change.
Having private declarations caused no problems, but it seems incorrect,
so it's fixed now and irrelevantPrivateDeclarations is added just in
case.

 #KT-41848 Fixed

compiler/testData/codegen/box/funInterface/irrelevantPrivateDeclarations.kt

@@ -0,0 +1,24 @@
+fun interface A {
+    fun invoke(s: String)
+
+    private fun privateFun() {}
+    private var privateProperty: String
+        get() = ""
+        set(value) {}
+
+    companion object {
+        fun s(a: A) {
+            a.invoke("OK")
+        }
+    }
+}
+
+fun test(f: (String) -> Unit) {
+    A.s(f)
+}
+
+fun box(): String {
+    var result = "Fail"
+    test { result = it }
+    return result
+}