fix: fix documentation rendered properly

[stevenhua0320]

@sbillinge ready to review. In this PR:

1. Fix documentation issues for diffpy.structure. This issue arises because as we add diffpy.utils as the dependencies for deprecator, when rendering the documentation, it couldn't find it internally and fails to render all classes that have deprecators. So, I made a mock-imports since the original documentation is not affected.
2. As we added a new parser p-vesta, when I run the package build api-doc, it auto-added all the new apis. I took a review for them and they are right.
   The new local documentation is shown below. I think they are rendering properly after this edit.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.20%. Comparing base (41c51ac) to head (87f8b12).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #192   +/-   ##
=======================================
  Coverage   99.20%   99.20%           
=======================================
  Files          15       15           
  Lines        2507     2507           
=======================================
  Hits         2487     2487           
  Misses         20       20           

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