allow get_entity_vals to ignore sidecars

[drammock]

closes #1351

PR Description

adds a new parameter ignore_suffixes to get_entity_vals so that sidecars (scans, coordsystem) may easily be ignored.

Merge checklist

Maintainer, please confirm the following before merging.
If applicable:

• All comments are resolved
• This is not your own PR
• All CIs are happy
• PR title starts with [MRG]
• whats_new.rst is updated
• New contributors have been added to CITATION.cff
• PR description includes phrase "closes <#issue-number>"

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.42%. Comparing base (8334fc6) to head (6fb4708).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1362      +/-   ##
==========================================
+ Coverage   97.40%   97.42%   +0.01%     
==========================================
  Files          40       40              
  Lines        8915     8922       +7     
==========================================
+ Hits         8684     8692       +8     
+ Misses        231      230       -1     

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[drammock]

All green, ready for review/merge

[sappelhoff]

Thanks a lot!