Support more chars in type URLs in the C++ text-format parser.

Change the C++ text-format parser to allow for more characters and formats
in the type URL prefixes of expanded Any protos. This follows a recent
change to the text-format spec which we are now closely following [1,2].

Note: This change modifies the default implementation of the `Finder` interface by removing [this special treatment](https://github.com/protocolbuffers/protobuf/blob/135bec4ee8c7cb8f9f8f2d5723bda5005948fa69/src/google/protobuf/text_format.cc#L255-L258) of non-standard type URLs. Any protos with type URL prefixes that are not `type.googleapis.com/` or `type.googleprod.com/` won't be treated specially anymore when converting to or from textproto using the default settings (for example, when using `TextFormat::PrintToString()` or `TextFormat::ParseFromString()`). In particular, Any protos with a non-standard type URL prefix will now get expanded by default when printed to textproto with the [`SetExpandAny()`](https://github.com/protocolbuffers/protobuf/blob/135bec4ee8c7cb8f9f8f2d5723bda5005948fa69/src/google/protobuf/text_format.h#L406) option enabled.

Refs:
- [1] https://protobuf.dev/reference/protobuf/textformat-spec/#characters
- [2] https://protobuf.dev/reference/protobuf/textformat-spec/#field-
PiperOrigin-RevId: 844790397

Author: protobuf-github-bot

src/google/protobuf/compiler/parser.cc

@@ -1666,6 +1666,10 @@ bool Parser::ParseOption(Message* options,
           return false;
         }
         break;
+
+      case io::Tokenizer::TYPE_URL_CHARS:
+        ABSL_LOG(FATAL) << "Unexpected token type (URL chars).";
+        return false;
     }
   }
 

src/google/protobuf/io/BUILD.bazel

@@ -140,6 +140,7 @@ cc_library(
         "@abseil-cpp//absl/log:absl_check",
         "@abseil-cpp//absl/log:absl_log",
         "@abseil-cpp//absl/strings",
+        "@abseil-cpp//absl/strings:charset",
         "@abseil-cpp//absl/strings:str_format",
     ],
 )