The compatibility baseline is now Java 17, which means we can use new language features and new bytecode version.
The MemSegBuffer implementation has been updated with the latest API changes from netty/main.
This is a step toward effectively eliminating reference counting.
Reference counting is only needed when the memory in buffers can be shared.
If we remove all forms of sharing, then the buffers would be in an owned state at all times.
Then we would no longer need to worry about the state of the buffers before calling, e.g. `ensureWritable` and methods like that.
Just removing `acquire` is not enough; we also need to remove the `slice` method.
In this commit we are, however, starting with `acquire` because doing so requires rearranging the type hierarchy and the generics we have in play.
This was not an easy exercise, but for the purpose of record keeping, it's useful to have that work separate from the work of removing `slice`.
