Add dask support

[tmi]

Compared to the original https://gitlab.com/ampx/aiml/ampx-fsql/-/merge_requests/11/diffs , there are a few changes:

• the lazy_errors has been introduced, and that complicated things a bit -- this is the convert lambda from the DaskReader.read_single etc
• the generics were introduced, but that does not affect with this one (the original comment about the generics being difficult in this particular case still stand)
• the handling of a missing end-/ has been handled differently, so that part of the code is not required anymore

but the core functionality is intact