HADOOP-19105. Improve resilience in vector reads.

[steveloughran]

Add a new releaser method, which then is invoked to release buffers on failure.

It is a bit contrived how we try not break external implementations when adding a new default implementation to PositionedReadable: the releaser will be lost unless they do so.

For code changes:

• [x] Does the title or this PR starts with the corresponding JIRA issue id (e.g. 'HADOOP-17799. Your PR title ...')?
• [ ] Object storage: have the integration tests been executed and the endpoint declared according to the connector-specific documentation?
• [ ] If adding new dependencies to the code, are these dependencies licensed in a way that is compatible for inclusion under ASF 2.0?
• [ ] If applicable, have you updated the LICENSE, LICENSE-binary, NOTICE-binary files?