Investigation/PoC: Emit references to actual DAE data in event documents

To support future use-cases where we may want to have access to "full" DAE data, rather than just a reduced scalar quantity, via something like _tiled_:

### Proof-of-concept

- Setup tiled using an ephemeral store (e.g. in-process memory only) for proof-of-concept.
- Get `SimpleDae` to emit references to histogram-mode data, in a way such that _tiled_ can return the full histogram mode data in a suitable python array format when asked
* This bit should be relatively standard, we know the shapes of histogram-mode data in advance - so is basically equivalent to how all the current x-ray facilities operate already.
- Get `SimpleDae` to emit references to event-mode data, in a way such that _tiled_ can return the full event mode data in a suitable python array format (e.g. `awkward-array`) when asked
* This bit will be harder - not sure how to currently do this as bluesky expects to know a "shape" up-front in the event descriptor, but for event-mode data we don't know that. **Likely to need discussion with upstream bluesky.**

### Notes

- For clarity "big data" (i.e. arrays) should never be in bluesky documents - only _references_ to the existing .nxs files
- This PoC can explicitly use an ephemeral / in-memory / in temp-directory tiled server for the moment. If/when we decide we need to bring in _tiled_ properly, then we can decide how to do that at that time.