Fix family external id participant grid filter

[dancoates]

• Rolls back changes to value filter introduced in Uplift code quality in metamist repo #957, this is just to allow for this quick fix, they can be re-added later when we have time to test and bugfix them
• Adds support for querying participant grid by family external id

[codecov]

Codecov Report

Attention: Patch coverage is 25.00000% with 6 lines in your changes missing coverage. Please review.

Project coverage is 81.54%. Comparing base (0d9e0bd) to head (78fbf83).
Report is 1 commits behind head on dev.

Files with missing lines	Patch %	Lines
db/python/tables/participant.py	25.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #982      +/-   ##
==========================================
- Coverage   81.56%   81.54%   -0.03%     
==========================================
  Files         184      184              
  Lines       15957    15965       +8     
==========================================
+ Hits        13016    13018       +2     
- Misses       2941     2947       +6     

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