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/privateClassVal.kt

@@ -4,7 +4,7 @@ import kotlin.reflect.jvm.accessible
 class Result {
     private val value = "OK"
 
-    fun ref() = Result::class.properties.single() as KProperty1<Result, String>
+    fun ref() = Result::class.memberProperties.single() as KProperty1<Result, String>
 }
 
 fun box(): String {