Improve standalone server killing on Windows

[philpax]

On Windows, Biome does not always manage to successfully shut down the server it spawns. I don't have a persistent repro for this yet, but I have seen Python servers running well after the client they came from was closed.

There are a few potential solutions to this:

• Have the server kill itself if it has no corresponding Biome running. We attempted this before, but found it rather brittle. Should reinvestigate.
• Have the client kill any zombie standalone servers that have the right "execution shape"
• Prevent more than one server running through lockfiles: if a lockfile is detected, either reassert control of the existing server or kill it and restart

Regardless of the path we take, we should make sure that it doesn't conflict with running in server mode, whether through the very same server-components directory or through another directory.