What is the purpose of the change

Currently, the Flink Avro format support for TIMESTAMP and TIMESTAMP_WITH_LOCAL_TIME_ZONE is capped at microsecond precision (6).
Standard Apache Avro (up to 1.11) only defines logical types for timestamp-millis and timestamp-micros.

When Flink tables utilize nanosecond precision (TIMESTAMP(9)), there is no native Avro logical type mapping, leading to either fallback behaviour (treating as raw BIGINT) or unsupported type exceptions during automatic schema conversion.

This pull request adds support for nanosecond-precision logical types (timestamp-nanos and local-timestamp-nanos) in the Flink Avro format. It also upgrades Avro to version 1.12.1 and enables decimal logical types handling for improved compatibility and numeric fidelity.

Specifically:

• Supports mapping Flink's TIMESTAMP(9) and TIMESTAMP_WITH_LOCAL_TIME_ZONE(9) back-and-forth with Avro's timestamp-nanos and local-timestamp-nanos logical types.
• Enables high-precision temporal calculations without losing precision at microsecond or millisecond boundaries.

Brief change log

• AvroToRowDataConverters.java:
  • Replaced the static timestamp converter with a precision-aware createTimestampConverter(int precision) that handles millisecond, microsecond, and nanosecond cases into TimestampData.
• RowDataToAvroConverters.java:
  • Updated conversion for TIMESTAMP_WITHOUT_TIME_ZONE and TIMESTAMP_WITH_LOCAL_TIME_ZONE to respect higher precision values up to 9 (nanoseconds) when packing epoch values.
• AvroSchemaConverter.java:
  • Mapped LogicalTypes.timestampNanos() and LogicalTypes.localTimestampNanos() schemas into equivalent Flink SQL styles (TIMESTAMP(9) / TIMESTAMP_WITH_LOCAL_TIME_ZONE(9)).
  • Updated conversion from Flink data types to Avro schema to support precision up to 9 for timestamp types.
• pom.xml:
  • Upgraded Avro dependency to 1.12.1.

Verifying this change

This change added tests and can be verified as follows:

• Updated unit tests within AvroSchemaConverterTest.java (e.g., asserting fields like type_timestamp_nanos, type_local_timestamp_nanos map correctly).
• Ran pre-existing Avro suite (AvroOutputFormatTest, AvroTypeExtractionTest) to ensure backwards compatibility with upgraded baseline versions.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): yes (Upgraded Avro to 1.12.1)
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: no
• The runtime per-record code paths (performance sensitive): yes (Adjusts converter inner-loops, standard for type feature additions)
• Anything that affects deployment or recovery: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? yes
• If yes, how is the feature documented? not applicable (Automatic type mapping addition, validated by updated test cases)