xlang-go: fetch from `zipURL` when present in `initializationOptions`
Created by: chrismwendt
This adds support to xlang-go for checking for a new zipURL
field in the initializationOptions
in the initialize
LSP request, and fetching the current repo's files from there if it's present. xlang-go will fall back to the old behavior of fetching from gitserver when that field is absent.
zipURL
will be constructed by lang-go and passed to Go buildserver through LSP Proxy (see the commit where I added it to lang-go).
This PR does not need to update the CHANGELOG because