[BUG] Rds does not handle mysql decimal data types when precision value is 19 or higher #6339

Describe the bug
Data Prepper RDS source does not handle MySQL DECIMAL data types with precision ≥19. When RDS exports snapshots to S3, values ≥2^63 are encoded as FIXED_LEN_BYTE_ARRAY in Parquet format (per AWS documentation). The NumericTypeHandler does not support this encoding, causing pipeline failures.

To Reproduce

1. Create MySQL table with DECIMAL(38,0) column containing values ≥2^63
2. Export RDS snapshot to S3
3. Configure Data Prepper pipeline with RDS source pointing to the export
4. Pipeline fails with error:

java.lang.IllegalArgumentException: Unsupported value type. The value is of type: class java.util.ArrayList
  at org.opensearch.dataprepper.plugins.source.rds.datatype.mysql.handler.NumericTypeHandler.handleNumericType

Expected behavior
RDS source should handle all MySQL DECIMAL types regardless of precision, converting FIXED_LEN_BYTE_ARRAY (ArrayList) to BigInteger for values that exceed INT64 range.

Screenshots
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Environment (please complete the following information):

• OS: [e.g. Ubuntu 20.04 LTS]
• Version [e.g. 22]

Additional context
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