SimMotor is not importable without dev dependencies

[callumforrester]

I can't do: from ophyd_async.sim.demo import SimMotor in a project that depends on ophyd-async.

File ~/projects/bluesky/bluesky-stomp/venv/lib64/python3.10/site-packages/ophyd_async/sim/demo/_pattern_detector/_pattern_generator.py:4
      1 from pathlib import Path
      2 from typing import AsyncGenerator, AsyncIterator, Dict, Optional
----> 4 import h5py
      5 import numpy as np
      6 from bluesky.protocols import DataKey, StreamAsset

ModuleNotFoundError: No module named 'h5py'

h5py is a dev dependency, so it should move into primary dependencies?

[coretl]

I'm erring on the side of a ophyd_async[sim] extra that includes h5py

[jwlodek]

Should we re-organize imports to allow for importing SimMotor without needing h5py? As I understand h5py is only necessary for the pattern generator sim device. So SimMotor maybe should be importable w/o needing this library?