[Java] Move ArrowBufPointer out of the java the memory package

The memory package is focused on memory access and management. ArrowBufPointer should be moved to algorithm package as it isn't core to the Arrow memory management primitives. I would further suggest that is an anti-pattern.

**Reporter**: [Jacques Nadeau](https://issues.apache.org/jira/browse/ARROW-7533) / @jacques-n
#### PRs and other links:
- [GitHub Pull Request apache/arrow#6208](https://github.com/apache/arrow/pull/6208)

_{**Note**: *This issue was originally created as [ARROW-7533](https://issues.apache.org/jira/browse/ARROW-7533). Please see the [migration documentation](https://github.com/apache/arrow/issues/14542) for further details.*}

まず PR #6208 を確認し、その後、Java のメモリおよびアルゴリズムパッケージ内で ArrowBufPointer とその参照を探します。移動後も参照とパッケージ構造に一貫性があることを確認し、プロジェクトが引き続き正常にビルドできることを検証します。

索引モデルが issue の本文から書いたものです。