gh-109888: Fix test_os _kill_with_event() on Windows (#110421)

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.