Ignore unselected subjects in BIDSLayoutIndexer

[tsalo]

Closes #3235.

Changes proposed in this pull request

• Incorporate a regular expression in the ignore list of the BIDSLayoutIndexer that flags subjects who are not in Config.participant_label (when provided).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 51.68%. Comparing base (ffc3810) to head (46e05b9).
Report is 12 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #3236       +/-   ##
===========================================
- Coverage   73.24%   51.68%   -21.57%     
===========================================
  Files          54       54               
  Lines        4160     4164        +4     
===========================================
- Hits         3047     2152      -895     
- Misses       1113     2012      +899     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[effigies]

I'm okay with this as-is. LMK if you want to try to improve the regex.

[effigies]

Okay, it looks like we are using re.search not re.match in pybids, which means we need to consider _, which is considered a word character.