Fix SIGINT handler to use sigaction with SA_ONSTACK flag

[NikolajBjorner]

Related to #7305

Update SIGINT signal handler to use sigaction with SA_ONSTACK flag.

• Replace signal function with sigaction function in src/util/scoped_ctrl_c.cpp to register the SIGINT handler.
• Set the SA_ONSTACK flag for the SIGINT signal handler in src/util/scoped_ctrl_c.cpp.
• Update on_ctrl_c function to use sigaction in src/util/scoped_ctrl_c.cpp.
• Modify scoped_ctrl_c struct in src/util/scoped_ctrl_c.h to include struct sigaction m_old_action instead of void (STD_CALL *m_old_handler)(int).

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