Fix inline question marking for content summaries

[jsharkey13]

We (still) have two different ways of working out whether a question has been answered correctly. This removes some of the duplication, to fix an issue where inline regions were overlooked when marking a question using the content summary way of marking.

The gameboard-based methods had already been updated to include inline regions, but collateQuestionPartIds(...) did not include them in its collation.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 34.38%. Comparing base (7024a46) to head (378fe94).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #630      +/-   ##
==========================================
- Coverage   34.40%   34.38%   -0.02%     
==========================================
  Files         514      514              
  Lines       23096    23086      -10     
  Branches     2794     2791       -3     
==========================================
- Hits         7946     7939       -7     
+ Misses      14350    14349       -1     
+ Partials      800      798       -2     

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

[mlt47]

This should achieve the same result as the removed code (but also account for inline questions).