Breaking change: Promote ExtensionRange to a proper class

PiperOrigin-RevId: 589938315

src/google/protobuf/descriptor.h

@@ -497,10 +497,7 @@ class PROTOBUF_EXPORT Descriptor : private internal::SymbolBase {
     // Never nullptr.
     const Descriptor* containing_type() const { return containing_type_; }
 
-#ifdef PROTOBUF_FUTURE_EXTENSION_RANGE_CLASS
-
    private:
-#endif
     int start_;
     int end_;
     const ExtensionRangeOptions* options_;

src/google/protobuf/port_def.inc

@@ -167,10 +167,6 @@ static_assert(PROTOBUF_ABSL_MIN(20230125, 3),
 // Owner: ezb@
 #define PROTOBUF_FUTURE_REMOVE_CONST_REPEATEDFIELD_GETARENA_API 1
 
-// Used to make ExtensionRange into a fully-fledged descriptor class.
-// Owner: mkruskal@
-#define PROTOBUF_FUTURE_EXTENSION_RANGE_CLASS 1
-
 // Used to lock down wrong ctype usages in proto file.
 // Owner: jieluo@
 #define PROTOBUF_FUTURE_REMOVE_WRONG_CTYPE 1