tests: Remove toxgen cutoff, add statsig

[sentrivana]

• a new integration was added and added to tox.ini, but not the template
• remove cutoff in favor of Define a proper deprecation policy for frameworks #4047

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.36%. Comparing base (c2a3c08) to head (eb7257a).
Report is 1 commits behind head on master.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4048      +/-   ##
==========================================
+ Coverage   80.32%   80.36%   +0.04%     
==========================================
  Files         140      140              
  Lines       15510    15510              
  Branches     2628     2628              
==========================================
+ Hits        12458    12465       +7     
+ Misses       2209     2202       -7     
  Partials      843      843              

see 2 files with indirect coverage changes