[j1wonpark]

Why are the changes needed?

Follow-up to #4378. Approach A uses the official Iceberg BOM to simplify dependency management while preserving the maintenance/connector version split.

This is an alternative to approach B, which introduces two Amoro BOMs.

Brief change log

• Import the official Iceberg BOM in the parent POM.
• Keep Iceberg 1.10.2 as the default and 1.8.1 for shared format and mixed-format modules.
• Remove redundant version declarations, retaining test JAR versions and a Flink 1.18 binding entry needed for partial builds with a newer connector Iceberg version.
• Preserve existing Parquet and Avro settings. No Java changes or new modules.

How was this patch tested?

• Dependency trees unchanged for Spark 3.3 (excluding AMS/dist), 3.4, and 3.5.
• 35 targeted test executions passed on JDK 11 before the final binding fix.
• After that fix, partial-build validation, full default validate, and dependency-tree comparison passed.
• Formatting checks and git diff --check passed.

The targeted tests were not rerun after the final POM fix. Full regression and end-to-end testing were not performed.