Add static reflection support for VIEW string_type fields.

PiperOrigin-RevId: 673033093

src/google/protobuf/unittest_string_view.proto

@@ -16,3 +16,15 @@ message TestStringView {
   repeated string repeated_string = 3;
   repeated bytes repeated_bytes = 4;
 }
+
+message TestStringViewExtension {
+  extensions 1 to max;
+}
+
+extend TestStringViewExtension {
+  string singular_string_view_extension = 1;
+  bytes singular_bytes_view_extension = 2;
+
+  repeated string repeated_string_view_extension = 3;
+  repeated bytes repeated_bytes_view_extension = 4;
+}