[Refactor](Multi Catalog) Unified meta cache framework with engine adapters

[suxiaogang223]

What problem does this PR solve?

Part of #60686

Summary

Introduce a unified metadata cache framework (UnifiedMetaCacheMgr) and migrate Paimon / Iceberg caches as the first two engine adapters.

Key Changes

• Add framework abstractions: UnifiedMetaCacheMgr, CatalogMetaCache, EngineMetaCache, CacheModule, CacheSpec
• Add engine adapters: PaimonEngineCache, IcebergEngineCache
• Refactor Paimon / Iceberg schema caching into snapshot cache (embed schema into snapshot cache value)
• Route PaimonUtils / IcebergUtils through engine cache
• Migrate remaining Iceberg call sites to engine cache path

Check List (For Reviewer who merge this PR)

• Confirm the release note
• Confirm test cases
• Confirm document
• Add branch pick label

[hello-stephen]

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[suxiaogang223]

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[hello-stephen]

FE Regression Coverage Report

Increment line coverage 22.21% (175/788) 🎉
Increment coverage report
Complete coverage report

[hello-stephen]

FE Regression Coverage Report

Increment line coverage 22.21% (175/788) 🎉
Increment coverage report
Complete coverage report

[suxiaogang223]

run external

[hello-stephen]

FE Regression Coverage Report

Increment line coverage 56.01% (578/1032) 🎉
Increment coverage report
Complete coverage report

[suxiaogang223]

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