[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.*}

Review PR #6208 first, then locate ArrowBufPointer and its references in the java memory and algorithm packages. Confirm the move leaves references and package structure consistent, and verify the project still builds successfully.

Written by the indexing model from the issue text.