[Java] Investigate dependency on Netty internals in arrow-memory-netty

### Describe the enhancement requested

See discussion in apache/arrow#36211.

Ideally we'd be able to remove the usage of internals, or at least make it so that they're optional (e.g. if we could implement two versions of InnerAllocator and pick the one that works at runtime).

### Component(s)

Java

Start with the arrow-memory-netty component and read the discussion in apache/arrow#36211. Trace its dependency on Netty internals and determine whether the usage can be removed or made optional at runtime. Done means the dependency is removed or an agreed optional implementation is established.

Written by the indexing model from the issue text.