[core] Maintain sorted primary-key index payloads

[JingsongLi]

Purpose

Maintain source-backed BTree and Bitmap payloads for one primary-key table bucket as compacted data files become active or inactive.

Changes

• Restore valid rotated payload groups for each active source data file and reject incomplete, stale, malformed, or mismatched groups.
• Track compacted source-file transitions and remove payloads whose source files are no longer active.
• Build uncovered source files asynchronously, with bounded retries and deterministic source ordering.
• Publish each rotated payload group atomically and delete stale, invalid, cancelled, or unpublished build output.
• Route payload-only updates to the append increment and data-compaction updates to the compact increment.
• Roll back source, payload, and pending-deletion state if a blocking commit is interrupted, and cancel the in-flight build.

Impact

This PR adds the bucket-local maintenance state machine only. Write-path coordination is intentionally left to the next PR. It uses the shared primary-key source policy, so complete fixed-bucket files produced by normal or Postpone Bucket compaction follow the same lifecycle.

Validation

• mvn -pl paimon-codegen-loader -am -Pfast-build -DskipTests package
• mvn -pl paimon-core -am -Pfast-build -DfailIfNoTests=false -DwildcardSuites=none -Dtest=BucketedSortedIndexMaintainerTest,PkSortedBucketIndexStateTest test (17 tests)
• mvn -pl paimon-core -DskipTests validate