Use cached namespace validation

[CodyCBakerPhD]

Fixes #917

Which came from dandi/helpdesk#43

Replaces #1036

Newest version of PyNWB supports validation against cached namespaces (and indeed this is now the default).

I've updated the usage here in a minimal way to both support older PyNWB versions (my other thought was to bump the version in the setup.cfg, but IDK what your policy or view is on that) that do not offer this feature as well as the newest version that supports it as a simple adjustment to the way the pynwb.validate function is called.

[codecov]

Codecov Report

Base: 88.27% // Head: 88.25% // Decreases project coverage by -0.01% ⚠️

Coverage data is based on head (d7ab706) compared to base (82b99ca).
Patch coverage: 57.14% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1149      +/-   ##
==========================================
- Coverage   88.27%   88.25%   -0.02%     
==========================================
  Files          73       73              
  Lines        8800     8803       +3     
==========================================
+ Hits         7768     7769       +1     
- Misses       1032     1034       +2     

Flag	Coverage Δ
unittests	88.25% <57.14%> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
dandi/pynwb_utils.py	82.81% <57.14%> (-0.67%)	⬇️

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[yarikoptic]

Thank you @CodyCBakerPhD and sorry I've missed it whenever you originally filed it. Looks good to me and is Green (freshier PRs aren't as lucky due to some disturbance in the Force). So I will not delay merging it as is. I think we can stick to not demand upgraded pynwb for a bit longer but might soon as well beef it up.