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 These changes were originally made in bitcoin/bitcoin#32387

[DrahtBot]

The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

Reviews

See the guideline for information on the review process.
A summary of reviews will appear here.

Conflicts

Reviewers, this pull request conflicts with the following ones:

• #237 (Made SpawnProcess() behavior safe post fork() by Sjors)
• #218 (Better error and log messages by ryanofsky)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

LLM Linter (✨ experimental)

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"]

^{drahtbot_id_5_m}

[DrahtBot]

🐙 This pull request conflicts with the target branch and needs rebase.