Expose builtin constraints

[WardBrian]

Closes #1436

Submission Checklist

• Run unit tests
• Documentation
  • If a user-facing facing change was made, the documentation PR is here: Forthcoming

Release notes

All the built-in constraint types now have corresponding _jacobian, _constrain, and _unconstrain functions. The first two functions are identical except for the _jacobian version will increment the target with the necessary change of variables adjustment.

Copyright and Licensing

By submitting this pull request, the copyright holder is agreeing to
license the submitted work under the BSD 3-clause license (https://opensource.org/licenses/BSD-3-Clause)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.55%. Comparing base (3aa50a9) to head (a407878).
Report is 17 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1494      +/-   ##
==========================================
+ Coverage   89.52%   89.55%   +0.02%     
==========================================
  Files          66       66              
  Lines        9684     9695      +11     
==========================================
+ Hits         8670     8682      +12     
+ Misses       1014     1013       -1     

Files with missing lines	Coverage Δ
src/frontend/Typechecker.ml	93.08% <100.00%> (+0.03%)	⬆️
src/stan_math_backend/Lower_expr.ml	93.65% <100.00%> (+0.08%)	⬆️

... and 1 file with indirect coverage changes

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[WardBrian]

The expression test failures are kind of weird but they seem to be fixed by stan-dev/math#3147 so there might just be some known bug in offset_multipliers code (cc @SteveBronder)

[SteveBronder]

I have a few small comments but overall I think good!