Issue #22018: Add _testcapi.raise_signal()

- Use _testcapi.raise_signal() in test_signal
- close also os.pipe() file descriptors in some test_signal tests where they
  were not closed properly
- Remove faulthandler._sigill() and faulthandler._sigbus(): reuse
  _testcapi.raise_signal() in test_faulthandler

Modules/_testcapimodule.c

@@ -11,6 +11,7 @@
 #include <float.h>
 #include "structmember.h"
 #include "datetime.h"
+#include <signal.h>
 
 #ifdef WITH_THREAD
 #include "pythread.h"
@@ -3063,6 +3064,24 @@ exit:
 }
 #endif   /* WITH_THREAD */
 
+static PyObject*
+test_raise_signal(PyObject* self, PyObject *args)
+{
+    int signum, err;
+
+    if (PyArg_ParseTuple(args, "i:raise_signal", &signum) < 0)
+        return NULL;
+
+    err = raise(signum);
+    if (err)
+        return PyErr_SetFromErrno(PyExc_OSError);
+
+    if (PyErr_CheckSignals() < 0)
+        return NULL;
+
+    Py_RETURN_NONE;
+}
+
 
 static PyMethodDef TestMethods[] = {
     {"raise_exception",         raise_exception,                 METH_VARARGS},
@@ -3198,6 +3217,8 @@ static PyMethodDef TestMethods[] = {
     {"docstring_with_signature_with_defaults",
         (PyCFunction)test_with_docstring, METH_NOARGS,
         docstring_with_signature_with_defaults},
+    {"raise_signal",
+     (PyCFunction)test_raise_signal, METH_VARARGS},
 #ifdef WITH_THREAD
     {"call_in_temporary_c_thread", call_in_temporary_c_thread, METH_O,
      PyDoc_STR("set_error_class(error_class) -> None")},