[jianguotian]

Purpose

Add Java-compatible bucket-first manifest sorting for fixed and postponed bucket tables, after the shared sorter (#854) and RowID support (#855).

Changes

• select bucket-first sorting for bucket > 0 and postponed bucket mode (bucket = -2)
• keep Data Evolution RowID sorting higher priority when complete RowID bounds exist
• sort entries by bucket, configured/default partition field, file kind, and file name
• use manifest bucket bounds when every input manifest provides them
• conservatively fall back to partition overlap when legacy manifests lack bucket bounds
• support non-partitioned fixed/postponed bucket tables

Merge order

Merge after #855. This replaces the closed bucket-only PR #852. The next PR will add the explicit manifest-compaction API.

Verification

• cargo fmt --check
• cargo test -p paimon --lib — 2,847 passed, 2 ignored
• dedicated tests for bucket-first entry order, legacy metadata fallback, RowID precedence, and non-partitioned bucket schemas

Related Java work

• [core] Support bucket-first sorting for manifest files paimon#9792
• [core] Support manifest sorting for non-partitioned bucketed tables paimon#9808