[Feature] Support 64-bit deletion vectors in Paimon C++

### Search before asking

- [x] I searched in the [issues](https://github.com/apache/paimon-cpp/issues) and found nothing similar.

### Motivation

### Motivation

Java Paimon supports both 32-bit and 64-bit deletion vectors through:

```properties
deletion-vectors.enabled=true
deletion-vectors.bitmap64=true

Paimon C++ currently exposes the deletion-vectors.bitmap64 option, but bitmap64 deletion vectors are not implemented:
- include/paimon/defs.h marks bitmap64 DV as unsupported.
- DeletionVector::Read recognizes the bitmap64 magic number but returns NotImplemented.
- Only BitmapDeletionVector, backed by RoaringBitmap32, is currently used for deletion-vector reads and writes.
As a result, Paimon C++ cannot read tables containing bitmap64 deletion vectors produced by Java Paimon, and cannot produce Iceberg-compatible deletion vectors.

### Solution

_No response_

### Anything else?

_No response_

### Are you willing to submit a PR?

- [x] I'm willing to submit a PR!

まず include/paimon/defs.h と DeletionVector::Read を通じて削除ベクトルの処理を追跡し、次に BitmapDeletionVector と RoaringBitmap32 の読み取り/書き込みパスを調べます。既存の bitmap32 の動作を bitmap64 のマジックナンバーおよび issue に記載されている Java Paimon のプロパティと比較します。Paimon C++ が Java で生成された bitmap64 の削除ベクトルを読み取り、Iceberg 互換のものを生成できれば完了です。

索引モデルが issue の本文から書いたものです。