Snappy Compression: Optimize DirectBuffer handling/release

The snappy compressor keeps buffers around even when they are not actively being used. When the buffer size is large this can lead to a lot of unneeded memory overhead.

**Reporter**: [Dale Richardson](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=tigerquoll) / @tigerquoll

_{**Note**: *This issue was originally created as [PARQUET-167](https://issues.apache.org/jira/browse/PARQUET-167). Please see the [migration documentation](https://issues.apache.org/jira/browse/PARQUET-2502) for further details.*}

The issue names no files or tests. Start by locating the Snappy compressor and its DirectBuffer allocation and release paths, then trace when buffers remain retained while inactive. Done means inactive large buffers are released without breaking compression behavior; add or update coverage for that lifecycle if the project has relevant tests.

Written by the indexing model from the issue text.