feat: Migrate bucket module

[lxy-9602]

Purpose

No Linked issue.

Migrate bucket ID calculation, bucket functions, and bucket select converter:

Bucket interfaces (include/paimon/bucket/):

• BucketIdCalculator — computes bucket ID for a given row (bucket_id_calculator.h)
• BucketFunctionType — enum for bucket function types (bucket_function_type.h)

Bucket functions (src/paimon/core/bucket/):

• BucketFunction — abstract bucket function interface (bucket_function.h)
• BucketIdCalculator — bucket ID calculation with hash-based routing (bucket_id_calculator.cpp)
• HiveBucketFunction — Hive-compatible bucket hash function (hive_bucket_function.h/cpp)
• HiveHasher — Hive ObjectInspector-compatible hashers for all data types (hive_hasher.h)
• ModBucketFunction — simple modulo-based bucket function (mod_bucket_function.h/cpp)
• DefaultBucketFunction — default bucket function using MurmurHash (default_bucket_function.h)
• BucketSelectConverter — converts predicates to bucket filter for scan pruning (bucket_select_converter.h/cpp)

Tests

• bucket_id_calculator_test.cpp — bucket ID calculation correctness
• hive_bucket_function_test.cpp — Hive bucket hash Java compatibility
• mod_bucket_function_test.cpp — modulo bucket function
• default_bucket_function_test.cpp — default bucket function
• bucket_select_converter_test.cpp — predicate to bucket filter conversion

API and Format

Documentation

Generative AI tooling

Migrate-by: Aone Copilot (Claude)

[lxy-9602]

Thank you @ChaomingZhangCN for contributing the bucket function framework, and @liangjie3138 for the BucketSelectConverter — migrated as part of this batch. 🎉

[leaves12138]

Thanks for migrating the bucket module. I reviewed PR #71 at head ba8560c200f768354b795290dd017225c1a671db.

Treating the remaining prerequisite dependency state as expected migration-period drift, I did not find a blocking correctness issue in the migrated bucket id calculator, default/mod/hive bucket functions, bucket select converter, Hive hasher, and related tests. I also checked the PR-local Decimal128 reconstruction change in bucket_id_calculator.cpp; it avoids shifting a signed negative high word and looks like a correct safety fix rather than a behavior regression.

Please make sure the dependent migration PRs are merged or rebased in, and run the relevant C++ build/tests from a clean checkout before final merge.