Allow --machine/--allow-embedding to be passed to devtools_tool serve

[DanTup]

The arg parser allows additional arguments, but not additional "options", so we need to add this explicitly* to allow --machine to work. The code already passes the extra args through to the server correctly, it just wasn't allowing this option to be provided on the command line.

* Or use the AllowAnythingParser, but looks like that would affect the existing options.

[DanTup]

(converted to draft... there are other flags we pass in VS Code like --try-ports we also need to support)

[DanTup]

Actually, I'm ditching --try-ports from VS Code since we're passing 10 which is the default value, but we did need allow-embedding.

[DanTup]

(this is ready for review now and hopefully the bots will be green 🤞)

[kenzieschmoll]

I'm surprised that these weren't passed through automatically since we pass any unhandled arguments along to the dds command. but lgtm

[DanTup]

I'm surprised that these weren't passed through automatically since we pass any unhandled arguments along to the dds command

I was too.. seems to be a difference between arguments and the named options. There's an AllowAnythingParser that would allow these, but I think we'd then have to also read the other options ourselves, so since we only need these two I figured this was better. We can always revisit if we want to pass more in future.