Daily Test Coverage Improver: Add comprehensive API pseudo-boolean constraint tests (#7898)

Added comprehensive test coverage for Z3's pseudo-boolean constraint API functions, improving coverage from 0% to 100% for src/api/api_pb.cpp.

- Created comprehensive test suite in src/test/api_pb.cpp
- Added test registration in src/test/main.cpp and src/test/CMakeLists.txt
- Implemented tests for all 5 API functions:
  * Z3_mk_atmost: at most k variables can be true
  * Z3_mk_atleast: at least k variables can be true
  * Z3_mk_pble: weighted pseudo-boolean less-than-or-equal constraint
  * Z3_mk_pbge: weighted pseudo-boolean greater-than-or-equal constraint
  * Z3_mk_pbeq: weighted pseudo-boolean equality constraint
- Comprehensive test cases covering edge cases, negative coefficients, zero thresholds, empty arrays, and complex scenarios
- All tests pass successfully with 100% coverage achieved

Coverage improvement: api_pb.cpp went from 0% (0/64 lines) to 100% (64/64 lines)

Co-authored-by: Daily Test Coverage Improver <github-actions[bot]@users.noreply.github.com>
Co-authored-by: Nikolaj Bjorner <nbjorner@microsoft.com>

src/test/main.cpp

@@ -176,6 +176,7 @@ int main(int argc, char ** argv) {
     TST(simple_parser);
     TST(api);
     TST(api_algebraic);
+    TST(api_pb);
     TST(api_datalog);
     TST(cube_clause);
     TST(old_interval);