Set 20-minute timeout for all CMake-based regression tests

[tautschnig]

Add TIMEOUT 1200 to the set_tests_properties call in both copies of the add_test_pl_profile macro (regression/CMakeLists.txt and regression/libcprover-cpp/CMakeLists.txt). This ensures CTest will kill and report as failed any regression test that exceeds 20 minutes, preventing CI jobs from hanging indefinitely on tests that time out.

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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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• My PR is restricted to a single feature or bugfix.
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[Copilot]

Pull request overview

Adds a per-test timeout to the regression test infrastructure to prevent CI hangs from long-running tests.

Changes:

• Enforce a 20-minute CTest timeout for CMake-registered regression tests.
• Add an optional -t / TESTPL_TIMEOUT timeout to regression/test.pl, implemented via fork + alarm + process-group kill.
• Update the test runner call chain to pass the timeout through to execution.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
regression/test.pl	Adds a per-test timeout option and enforces it by killing the test process group on timeout.
regression/CMakeLists.txt	Adds TIMEOUT 1200 to CTest properties for regression tests.
regression/libcprover-cpp/CMakeLists.txt	Adds TIMEOUT 1200 to CTest properties for regression tests in libcprover-cpp.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.01%. Comparing base (eaaf029) to head (3780790).
⚠️ Report is 7 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #8848   +/-   ##
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  Coverage    80.01%   80.01%           
========================================
  Files         1700     1700           
  Lines       188338   188338           
  Branches        73       73           
========================================
+ Hits        150695   150699    +4     
+ Misses       37643    37639    -4     

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