Support member extension properties, implement KClass.getExtensionProperties()

#KT-6570 Fixed

compiler/testData/codegen/boxWithJava/reflection/kotlinPropertyInheritedInJava/J.java

@@ -0,0 +1,2 @@
+public class J extends K {
+}

compiler/testData/codegen/boxWithJava/reflection/kotlinPropertyInheritedInJava/K.kt

@@ -0,0 +1,40 @@
+import kotlin.reflect.*
+import kotlin.reflect.jvm.*
+
+public open class K {
+    var prop: String = ":("
+
+    val Int.ext: Int get() = this
+}
+
+fun box(): String {
+    val j = J()
+
+    val prop = J::prop
+    if (prop !is KMutableMemberProperty<*, *>) return "Fail instanceof"
+    if (prop.name != "prop") return "Fail name: ${prop.name}"
+    if (prop.get(j) != ":(") return "Fail get before: ${prop[j]}"
+    prop[j] = ":)"
+    if (prop.get(j) != ":)") return "Fail get after: ${prop[j]}"
+
+
+    if (prop == K::prop) return "Fail J::prop == K::prop (these are different properties)"
+
+
+    val klass = javaClass<J>().kotlin
+    val prop2 = klass.getProperties().firstOrNull { it.name == "prop" }
+                ?: "Fail: no 'prop' property in getProperties()"
+    if (prop != prop2) return "Fail: property references from :: and from getProperties() differ"
+    if (prop2 !is KMutableMemberProperty<*, *>) return "Fail instanceof 2"
+    (prop2 as KMutableMemberProperty<J, String>).set(j, "::)")
+    if (prop.get(j) != "::)") return "Fail get after 2: ${prop[j]}"
+
+
+    val ext = klass.getExtensionProperties().firstOrNull { it.name == "ext" }
+              ?: "Fail: no 'ext' property in getProperties()"
+    ext as KMemberExtensionProperty<J, Int, Int>
+    val fortyTwo = ext.get(j, 42)
+    if (fortyTwo != 42) return "Fail ext get: $fortyTwo"
+
+    return "OK"
+}