buffer: simplify buffer API

[jknack]

• simplify (probably remove) buffer API
  • We just need something that allow us to use netty buffers and/or undertow/jetty buffer pools

[agentgt]

@jknack let me know what you decide or link PRs if you can. I may have to adjust the jstachio module. I have a plethora of output options: https://jstach.io/doc/jstachio/current/apidocs/io.jstach.jstachio/io/jstach/jstachio/output/package-summary.html

Have a happy holidays!