Add windows support

[ryanofsky]

Add support for running on windows. These changes make the libmultiprocess API more generic, using stream types instead of file descriptors. All features are supported, including spawning processes with socket connections to the parent process. These changes were originally made in bitcoin/bitcoin#32387

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Possible typos and grammar issues:

• analagous -> analogous [spelling mistake in comment; should be "analogous"]
• being being -> being [duplicated word in comment, makes the sentence awkward/incomprehensible]
• named path pipe -> named pipe [redundant/incorrect phrasing; likely meant "named pipe"]

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