Warn when unexpected keys in specs

[rly]

Motivation

In a few separate instances, users have tried to create an extension with a group, dataset, or link with "required: true" or an attribute with "quantity: '?'" (I'm not 100% sure on this latter one but definitely the former one). The extension template now warns if the yaml fails schema validation. It would be useful to do this in the API as well. Right now, extra args to the spec constructors are ignored. This PR warns when reading a spec with extra args. We could make this an error, but I worry about breaking the reading of existing data with extensions that have extra args.

Ref: catalystneuro/ndx-patterned-ogen#15 (comment)

Checklist

• Did you update CHANGELOG.md with your changes?
• Does the PR clearly describe the problem and the solution?
• Have you reviewed our Contributing Guide?
• Does the PR use "Fix #XXX" notation to tell GitHub to close the relevant issue numbered XXX when the PR is merged?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.78%. Comparing base (539ecf4) to head (492e061).
Report is 27 commits behind head on dev.

Additional details and impacted files

@@           Coverage Diff           @@
##              dev    #1134   +/-   ##
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  Coverage   88.78%   88.78%           
=======================================
  Files          45       45           
  Lines        9778     9782    +4     
  Branches     2777     2778    +1     
=======================================
+ Hits         8681     8685    +4     
  Misses        780      780           
  Partials      317      317           

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