Automatically move server config file to build output

[nicohrubec]

This only needs to happen for nitro, since for other hosting providers we have a different setup.

For nitro we need to move instrument.server.mjs to .output/server.

[linear]

JS-1384

[nicohrubec]

Got started on this a while back: #19104

Updating this PR to a mergable state should be relatively low effort.