Default linear-memory backend (Elixir-facing name), a thin shim over the
Erlang :wa_embedder_memory_binary implementation. Retained so the
WaEmbedder.Memory.Binary name and its direct API stay callable from Elixir
(and so WaEmbedder.Memory.validate_backend!/1 sees all nine callbacks
exported here).
The reference is the opaque %{mem: binary, max: max | :none} map produced
by the Erlang backend; out-of-bounds access traps via
:erlang.error({:wasm_trap, :memory_oob, %{addr: addr, width: width}}).