bpo-40826: Fix test_repl.test_close_stdin() on Windows (GH-20779)

test_repl.test_close_stdin() now calls
support.suppress_msvcrt_asserts() to fix the test on Windows.

* Move suppress_msvcrt_asserts() from test.libregrtest.setup to
  test.support. Make its verbose parameter optional: verbose=False by
  default.
* Add msvcrt.GetErrorMode().
* SuppressCrashReport now uses GetErrorMode() and SetErrorMode() of
  the msvcrt module, rather than using ctypes.
* Remove also an unused variable (deadline) in wait_process().