PR Summary

Fix #24986

This is a follow-up fix to the changes introduced by #20853.

• If we are starting a process with a new window, we should leave the standard handles unset when they are not redirected and let Windows figure out the default to use creating the process. Otherwise, the standard input of the new window will be tied with the old window for some reason and causes the new window to be unusable.
• If we are starting a process re-using the current window (with -NoNewWindow), then we need to explicitly set all the standard handles, especially when any of them is redirected. Otherwise, the un-redirected handles will become invalid.

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