Review Netty 5 buffer API

There's a proposed new buffer API for Netty 5: https://github.com/netty/netty-incubator-buffer-api/blob/070ffa26885ee078f364ad0334c9b177442f370b/RATIONALE.adoc. We should take a look at it and see if it will affect Aleph/Manifold and provide comment if so.

Read the linked Netty 5 buffer API RATIONALE.adoc first, then inspect how Aleph and Manifold use Netty buffers. Determine whether the proposed API affects either project and document the findings in a comment, including any compatibility concerns.

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