Split resource assemblies into their own VSIXs automatically

Several repos, including dotnet/roslyn, ship their resource assemblies by just including them in the main VSIX they insert into the VS build. This works and is reasonably simple but means customers get resource assemblies for languages they don't care about. This incurs some time and disk space cost when downloading and installing the extra assemblies.

It would be very helpful if Arcade could automatically move the localized resources out of the main VSIX and into a set of per-locale VSIXs, with the main VSIX having an optional dependency on those. This way users only get the resource assemblies corresponding to their selected lang packs.