Remove support for CVC 3 and CVC 4

[kroening]

This removes the support for CVC 3 and CVC 4.

CVC 3 and 4 have been superseded by CVC 5.

• Each commit message has a non-empty body, explaining why the change was made.
• n/a Methods or procedures I have added are documented, following the guidelines provided in CODING_STANDARD.md.
• The feature or user visible behaviour I have added or modified has been documented in the User Guide in doc/cprover-manual/
• n/a Regression or unit tests are included, or existing tests cover the modified code (in this case I have detailed which ones those are in the commit message).
• n/a My commit message includes data points confirming performance improvements (if claimed).
• My PR is restricted to a single feature or bugfix.
• n/a White-space or formatting changes outside the feature-related changed lines are in commits of their own.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.50%. Comparing base (1b41bbe) to head (62a9c66).
⚠️ Report is 2 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #8967      +/-   ##
===========================================
- Coverage    81.06%   80.50%   -0.56%     
===========================================
  Files         1704     1704              
  Lines       210005   188778   -21227     
  Branches        73       73              
===========================================
- Hits        170235   151974   -18261     
+ Misses       39770    36804    -2966     

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[tautschnig]

I'd agree with CVC 3 and CVC 4, but Yices last released on 2025-07-16, see https://github.com/SRI-CSL/yices2/releases/tag/yices-2.7.0. Compare that to Boolector, which has the repository marked as "archived" and last released in August 2024.