codeintel: Add policies package
Created by: efritz
This PR adds a package that will take the place of the current state of the art for matching policies against a git commit graph.
The idea is to have a central place to compare policies against the current state of a repository and/or its LSIF data. The package in this PR support (in an unpublished branch):
- a GraphQL preview resolver
- a rewrite of the upload expirer job
- a rewrite of the index scheduler job
This package now contains ALL the logic necessary to expand a set of policies into matching commits and should be completely unit-testable. Please take a close look at logic and tests.