Remove deprecated add_axioms_for_concat_code_point method

[tautschnig]

Inline the body of the deprecated add_axioms_for_concat_code_point method at its sole call site in add_axioms_for_function_application. This removes the method declaration from the header and the separate method definition while preserving the functionality needed by JBMC's StringBuilder.appendCodePoint and StringBuffer.appendCodePoint.

Fixes: #8014

Co-authored-by: Kiro kiro-agent@users.noreply.github.com

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• n/a The feature or user visible behaviour I have added or modified has been documented in the User Guide in doc/cprover-manual/
• 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).
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[Copilot]

Pull request overview

This PR removes the deprecated string_constraint_generatort::add_axioms_for_concat_code_point helper by inlining its implementation at its only call site inside add_axioms_for_function_application, preserving behavior used by JBMC’s StringBuilder.appendCodePoint / StringBuffer.appendCodePoint handling (Fixes #8014).

Changes:

• Removed the deprecated add_axioms_for_concat_code_point declaration from the generator header.
• Inlined the former implementation directly into the ID_cprover_string_concat_code_point_func dispatch branch.
• Deleted the obsolete definition from string_concatenation_builtin_function.cpp.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
src/solvers/strings/string_constraint_generator.h	Drops the deprecated method declaration from the public API surface of the generator class.
src/solvers/strings/string_constraint_generator_main.cpp	Inlines the concat-code-point axiom generation logic into the function-application dispatcher.
src/solvers/strings/string_concatenation_builtin_function.cpp	Removes the deprecated method definition that is no longer referenced.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.45%. Comparing base (6df204e) to head (c3d113d).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #8924      +/-   ##
===========================================
- Coverage    80.46%   80.45%   -0.01%     
===========================================
  Files         1704     1704              
  Lines       188665   188665              
  Branches        73       73              
===========================================
- Hits        151805   151799       -6     
- Misses       36860    36866       +6     

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