Fix issue with resolving attribute specs with same name

[rly]

Motivation

Fix #1121

How to test the behavior?

See new tests

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

Attention: Patch coverage is 64.06250% with 23 lines in your changes missing coverage. Please review.

Project coverage is 88.79%. Comparing base (9387e85) to head (f139d0c).
Report is 31 commits behind head on dev.

Files with missing lines	Patch %	Lines
src/hdmf/spec/spec.py	64.06%	14 Missing and 9 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #1122      +/-   ##
==========================================
- Coverage   88.86%   88.79%   -0.08%     
==========================================
  Files          45       45              
  Lines        9774     9774              
  Branches     2776     2776              
==========================================
- Hits         8686     8679       -7     
- Misses        774      778       +4     
- Partials      314      317       +3     

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