Zarr backing MDA display can overflow disk space - maybe make location configurable

[ianhi]

In #145 (review) @tlambert03 noted

In the future, it'd be nice to bring back the in-memory behavior as well if someone knows they won't be exceeding their RAM (along with checks to let you know whether you would be).

In that same vein it turns out you can also muck things up by running out of hard drive space :(

We have a multi-terabyte data drive on that computer which is where I save images, but the zarr location isn't configurable to use that directory. Interestingly since the saving mechanism is separate and uses the other drive it appears to continue functioning.

I think there are two opportunities for improvement here:

1. Prevention: Allow some configurability in where the temp files are made
2. Damage control: Catch and raise a Napari dialog with the error.