Fix issue with resolving attribute specs with same name

[rly]

Motivation

Fix #1121

How to test the behavior?

See new tests

Checklist

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

[codecov[bot]]

Codecov Report

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

Project coverage is 88.79%. Comparing base (9387e85) to head (f139d0c).

Files	Patch %	Lines
src/hdmf/spec/spec.py	64.06%	14 Missing and 9 partials :warning:

Additional details and impacted files

```diff @@ 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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