fix: do not end process in middleware mode, fix #4196 #4232
It doesn't make much sense to end the vite process based on stdin when vite is running in middleware mode, as pointed out in #4196.
I based the original check for CI off of what create-react-app does, but that project does not have a specific "middleware mode". I think it makes sense to include both of these checks, until/unless we can find a good way to detect running in docker/CI/container/non-interactive terminal (which is harder than it seems like it should be).
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