Bump linkedin/iceberg to 1.2.0.23 / 1.5.2.20 (ORC initial-defaults)

[cbb330]

Summary

Bumps both OpenHouse Iceberg pins so Spark 3.1 and Spark 3.5 pick up the ORC/Spark initial-default read path (idToConstant) and the complete-embedded-field-id omit rule.

• iceberg_1_2_version: 1.2.0.20 → 1.2.0.23 (published as v1.2.0.23)
• iceberg_1_5_version: 1.5.2.17 → 1.5.2.20 (next two Shipkit tags after current v1.5.2.18, once linkedin/iceberg#273 then linkedin/iceberg#274 merge)

CI is expected to fail resolving 1.5.2.20 until those Iceberg PRs merge and Shipkit publishes the tags. Rerun CI after v1.5.2.20 exists. Does not include linkedin/iceberg#269.

Changes

• Client-facing API Changes
• Internal API Changes
• Bug Fixes
• New Features
• Performance Improvements
• Code Style
• Refactoring
• Documentation
• Tests

Spark/ORC readers fill missing columns from Iceberg initial defaults via idToConstant, and skip that fill only when the file already embeds a complete field-id set.

1.2 line: linkedin/iceberg#267 (v1.2.0.22) and linkedin/iceberg#268 (v1.2.0.23), plus CI-only linkedin/iceberg#266 (v1.2.0.21).

1.5 line: linkedin/iceberg#257 is already v1.5.2.18; #273 / #274 are the 1.5 twins of #267 / #268 and become v1.5.2.19 / v1.5.2.20 if they are the next two merges on openhouse-1.5.2.

Testing Done

• Manually Tested on local docker setup. Please include commands ran, and their output.
• Added new tests for the changes made.
• Updated existing tests to reflect the changes made.
• No tests added or updated. Please explain why. If unsure, please feel free to ask for help.
• Some other form of testing like staging or soak time in production. Please explain.

Version pin only. Iceberg coverage lives in linkedin/iceberg #267/#268 and #273/#274.

Additional Information

• Breaking Changes
• Deprecations
• Large PR broken into smaller PRs, and PR plan linked in the description.

Depends on merge order 273 then 274 on linkedin/iceberg (openhouse-1.5.2). Retarget 274 onto openhouse-1.5.2 after 273 lands. If another openhouse-1.5.2 PR merges first, the 1.5 pin needs to move to the actual tag that contains #274.