gh-111495: Add PyFile tests (#129449)

Add tests for the following functions in test_capi.test_file:

* PyFile_FromFd()
* PyFile_GetLine()
* PyFile_NewStdPrinter()
* PyFile_WriteObject()
* PyFile_WriteString()
* PyObject_AsFileDescriptor()

Add Modules/_testlimitedcapi/file.c file.

Remove test_embed.StdPrinterTests which became redundant.

Lib/test/test_embed.py

@@ -1985,56 +1985,5 @@ class MiscTests(EmbeddingTestsMixin, unittest.TestCase):
         self.assertIn("unique-python-message", out)
 
 
-class StdPrinterTests(EmbeddingTestsMixin, unittest.TestCase):
-    # Test PyStdPrinter_Type which is used by _PySys_SetPreliminaryStderr():
-    #   "Set up a preliminary stderr printer until we have enough
-    #    infrastructure for the io module in place."
-
-    STDOUT_FD = 1
-
-    def create_printer(self, fd):
-        ctypes = import_helper.import_module('ctypes')
-        PyFile_NewStdPrinter = ctypes.pythonapi.PyFile_NewStdPrinter
-        PyFile_NewStdPrinter.argtypes = (ctypes.c_int,)
-        PyFile_NewStdPrinter.restype = ctypes.py_object
-        return PyFile_NewStdPrinter(fd)
-
-    def test_write(self):
-        message = "unicode:\xe9-\u20ac-\udc80!\n"
-
-        stdout_fd = self.STDOUT_FD
-        stdout_fd_copy = os.dup(stdout_fd)
-        self.addCleanup(os.close, stdout_fd_copy)
-
-        rfd, wfd = os.pipe()
-        self.addCleanup(os.close, rfd)
-        self.addCleanup(os.close, wfd)
-        try:
-            # PyFile_NewStdPrinter() only accepts fileno(stdout)
-            # or fileno(stderr) file descriptor.
-            os.dup2(wfd, stdout_fd)
-
-            printer = self.create_printer(stdout_fd)
-            printer.write(message)
-        finally:
-            os.dup2(stdout_fd_copy, stdout_fd)
-
-        data = os.read(rfd, 100)
-        self.assertEqual(data, message.encode('utf8', 'backslashreplace'))
-
-    def test_methods(self):
-        fd = self.STDOUT_FD
-        printer = self.create_printer(fd)
-        self.assertEqual(printer.fileno(), fd)
-        self.assertEqual(printer.isatty(), os.isatty(fd))
-        printer.flush()  # noop
-        printer.close()  # noop
-
-    def test_disallow_instantiation(self):
-        fd = self.STDOUT_FD
-        printer = self.create_printer(fd)
-        support.check_disallow_instantiation(self, type(printer))
-
-
 if __name__ == "__main__":
     unittest.main()