Implements getter functions for LFMCMC

[apulsipher]

Implement get_params_mean() and get_stats_mean() functions for LFMCMC and add to tests

Also, fix a sizing bug in the set_summary_fun_cpp that causes res to be too large when the summary fun output was smaller than dat

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 34.38%. Comparing base (bf4b679) to head (86b2e41).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #49      +/-   ##
==========================================
+ Coverage   34.03%   34.38%   +0.34%     
==========================================
  Files          36       36              
  Lines        1898     1908      +10     
==========================================
+ Hits          646      656      +10     
  Misses       1252     1252              

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

---

🚨 Try these New Features:

• Flaky Tests Detection - Detect and resolve failed and flaky tests