Write RFC for precise code intel mono repo support

Created by: shrouxm

Currently our tooling & docs are written assuming the user will be uploading LSIF indexes for the entire repo on each commit. This works for repos with a small number of projects, but would probably make precise code intel unusable on a large monorepo 10s or 100s of projects. This issue is to create an RFC drawing on RFC 101 proposing tooling features to address this use case.