[Stan 2.32] Delay expiring syntax deprecations one version

[WardBrian]

Following discussions on the forums this PR is prepared as an alternative to #1287 for this version which moves the removal version of syntax changes back to 2.33. This should avoid a situation where it is impossible to write Stan programs which can't be compiled by both RStan and CmdStan.

Submission Checklist

• Run unit tests
• Documentation
  • If a user-facing facing change was made, the documentation PR is here: Update documentation for delayed deprecation removals docs#629

Release notes

Syntax removals scheduled for this version have been pushed back to 2.33. We still recommend updating your Stan models as you are able. As a reminder, deprecated syntax which will be removed in minor versions can as a rule be updated automatically using find-and-replace tools or the Stan compiler's auto-formatting abilities.

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)

[WardBrian]

@andrjohns I assume it is okay to remove the command-line arguments we had deprecated for this version still, right?

[codecov]

Codecov Report

Merging #1303 (d089a82) into master (06679e7) will decrease coverage by 0.04%.
The diff coverage is 50.00%.

@@            Coverage Diff             @@
##           master    #1303      +/-   ##
==========================================
- Coverage   89.09%   89.06%   -0.04%     
==========================================
  Files          64       64              
  Lines        9758     9756       -2     
==========================================
- Hits         8694     8689       -5     
- Misses       1064     1067       +3     

Impacted Files	Coverage Δ
src/frontend/Input_warnings.ml	85.00% <ø> (ø)
src/frontend/Typechecker.ml	89.87% <ø> (ø)
src/stanc/stanc.ml	81.96% <33.33%> (-2.59%)	⬇️
src/frontend/Deprecation_analysis.ml	92.30% <100.00%> (ø)
src/middle/Stan_math_signatures.ml	98.05% <100.00%> (-0.01%)	⬇️

[WardBrian]

@rok-cesnovar this will need to go in before the freeze (I think we have a checklist item on the release checklist for this kind of thing, but just double-checking)

[nhuurre]

#1287 doesn't just remove syntax, it has a couple of fixes that could go here as well

• add deprecation warnings to stancjs

  stanc3/src/stancjs/stancjs.ml

  Lines 58 to 61 in 4e3305e

  	let deprecation_warnings =
  	if canonicalizer_settings.deprecations then []
  	else Deprecation_analysis.collect_warnings typed_ast in
  	let warnings = warnings @ deprecation_warnings in

• add lkj_cov_lpdf:

  stanc3/src/middle/Stan_math_signatures.ml

  Line 255 in 042c649

  ; ([Lpdf; Log], "lkj_cov", [DMatrix; DVector; DVector; DReal], AoS)

[andrjohns]

@andrjohns I assume it is okay to remove the command-line arguments we had deprecated for this version still, right?

Yep that should be fine AFAIK. I'll run the rstan & StanHeaders unit tests with this stanc and open a PR for rstan with anything we'll need to update internally