tests: Move sanic under toxgen & add option to control how many releases to pick

[sentrivana]

• Move sanic under toxgen
• This gets rid of the -latest group for Web 2 as all Web 2 test suites are now governed by toxgen
• Add num_versions as a new option to optionally slim down the number of tested versions (useful for sanic as it has a lot of "majors" due to calver)
• When a package had multiple majors, we used to always pick the lowest as well as the highest release in the last major -- removed the lowest now to not over-test. All majors will still be tested by default, we just won't be testing two releases in the last major.

Ref #4506

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.56%. Comparing base (7ae6866) to head (70df254).
⚠️ Report is 1 commits behind head on master.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4767      +/-   ##
==========================================
- Coverage   84.58%   84.56%   -0.02%     
==========================================
  Files         158      158              
  Lines       16521    16521              
  Branches     2867     2867              
==========================================
- Hits        13974    13971       -3     
  Misses       1703     1703              
- Partials      844      847       +3     

see 3 files with indirect coverage changes

[sl0thentr0py]

instead of a heuristic, should we explicitly add a "calver": True field in the config?

[sentrivana]

Hmm that's maybe a bit too specific but maybe a key with a numerical value to define how many versions should be tested? That could then be also used for some of the smaller integrations to test less versions since now it's a bit of an overkill for some

[sentrivana]

I'll add smth 👍🏻

[sentrivana]

Updated, see #4767 (comment)