Shouldn't load apollo-upload-server if uploads are disabled

[Akryum]

If uploads option is false on ApolloServer constructor options, the apollo-upload-server module is still loaded. On some node versions, this causes issues like core-js not being found.

This would help close vuejs/vue-cli#2215 (we don't need file uploads for vue cli ui).

[Akryum]

I believe https://github.com/jaydenseric/apollo-upload-server/releases/tag/v6.0.0-alpha.1 would fix the issue but it's still in alpha.

[yofriadi]

#1542

[abernix]

@Akryum It does seem wise to avoid loading apollo-upload-server if uploads are disabled, but I think the overall issue with core-js has been fixed now, as explained in #1542 (comment).

Should we keep this open? (I think a PR that conditionally requires apollo-upload-server would be welcome, but it seems less urgent without the core-js issue at play.)

[martijnwalraven]

I actually already did this as part of a PR for running Apollo Server on edge. I'll pick that work up later, but I've just merged those commits to get this in and avoid the PR from getting out of sync.