Rename KClass.properties and extensionProperties: prepend 'member'

To better emphasize the fact that all returned properties require an instance
of the class they are declared in. Another issue was that
'Some::class.extensionProperties' was sometimes incorrectly perceived as
"get all extension properties available on the class Some"

compiler/testData/codegen/boxWithStdlib/reflection/properties/getPropertiesMutableVsReadonly.kt

@@ -6,7 +6,7 @@ class A(val readonly: String) {
 }
 
 fun box(): String {
-    val props = javaClass<A>().kotlin.properties
+    val props = javaClass<A>().kotlin.memberProperties
     val readonly = props.single { it.name == "readonly" }
     assert(readonly !is KMutableProperty1<A, *>) { "Fail 1: $readonly" }
     val mutable = props.single { it.name == "mutable" }