[3.12] gh-109888: Fix test_os _kill_with_event() on Windows (GH-110421)

[miss-islington]

Replace os.kill() with proc.kill() which catchs PermissionError.

Rewrite _kill_with_event():

• Use subprocess context manager ("with proc:").
• Use sleeping_retry() to wait until the child process is ready.
• Replace SIGINT with proc.kill() on error.
• Replace 10 seconds with SHORT_TIMEOUT to wait until the process is
  ready.
• Replace 0.5 seconds with SHORT_TIMEOUT to wait for the process
  exit.
  (cherry picked from commit aaf297c)

Co-authored-by: Victor Stinner [email protected]

• Issue: test_os.Win32KillTests: test_CTRL_BREAK_EVENT() failed on GHA Windows x64 #109888