Check for positive indices on stochastic matrices, sum to zero types

[WardBrian]

Fixes stan-dev/stan#3366. We should also update the deserializer so it actually catches these if they do sneak through the compiler, though.

Submission Checklist

• Run unit tests
• Documentation
  • If a user-facing facing change was made, the documentation PR is here:
  • OR, no user-facing changes were made

Release notes

Fixed the some of the newer constraint types not having sufficient size checks for their declarations.

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

❌ Patch coverage is 88.88889% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 90.28%. Comparing base (a09b85c) to head (31e2bde).
⚠️ Report is 9 commits behind head on master.

Files with missing lines	Patch %	Lines
src/middle/Internal_fun.ml	50.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1563   +/-   ##
=======================================
  Coverage   90.27%   90.28%           
=======================================
  Files          65       65           
  Lines        9988     9992    +4     
=======================================
+ Hits         9017     9021    +4     
  Misses        971      971           

Files with missing lines	Coverage Δ
src/frontend/Ast_to_Mir.ml	93.94% <100.00%> (+0.04%)	⬆️
src/stan_math_backend/Lower_stmt.ml	95.65% <100.00%> (ø)
src/middle/Internal_fun.ml	63.15% <50.00%> (ø)

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