feat(types): support CHAR/VARCHAR/BINARY/VARBINARY in data type json parser

Previously CHAR/VARCHAR/BINARY/VARBINARY were registered as keywords but had
no handling branch in ParseTypeByKeyword, so deserializing a schema that
contained them failed with "Unsupported type: VARCHAR". Map CHAR/VARCHAR to
arrow::utf8() and BINARY/VARBINARY to arrow::binary() (consistent with STRING
and BYTES), parsing and discarding the optional length parameter. Add parser
test cases covering these types with and without a length argument.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: SteNicholas

src/paimon/common/types/data_type_json_parser.cpp

@@ -465,6 +465,12 @@ Result<std::shared_ptr<arrow::DataType>> TokenParser::ParseTypeWithNullability(b
 Result<std::shared_ptr<arrow::DataType>> TokenParser::ParseTypeByKeyword(bool* is_blob) {
     PAIMON_RETURN_NOT_OK(NextToken(TokenType::KEYWORD));
     switch (TokenAsKeyword()) {
+        case Keyword::CHAR:
+        case Keyword::VARCHAR:
+            return ParseStringType<arrow::StringType>();
+        case Keyword::BINARY:
+        case Keyword::VARBINARY:
+            return ParseStringType<arrow::BinaryType>();
         case Keyword::BYTES:
             return arrow::binary();
         case Keyword::BLOB: {

src/paimon/common/types/data_type_json_parser_test.cpp

@@ -111,6 +111,14 @@ TEST(DataTypeJsonParserTest, ParseTypeAtomicTypeSuccess) {
         {"TIMESTAMP_LTZ(9)", arrow::timestamp(arrow::TimeUnit::NANO, timezone)},
         {"BYTES", arrow::binary()},
         {"STRING", arrow::utf8()},
+        {"CHAR", arrow::utf8()},
+        {"CHAR(10)", arrow::utf8()},
+        {"VARCHAR", arrow::utf8()},
+        {"VARCHAR(10)", arrow::utf8()},
+        {"BINARY", arrow::binary()},
+        {"BINARY(10)", arrow::binary()},
+        {"VARBINARY", arrow::binary()},
+        {"VARBINARY(10)", arrow::binary()},
     };
 
     for (const auto& test_case : test_cases) {