codeintel: Limit size of commit graph

Created by: efritz

When calculating the set of uploads for each commit, we now only bring back the portion of the commit graph that has LSIF data and will be reasonably queried. This greatly reduces the number of commits that we need to calculate upload visibility for and will reduce the memory requirements (see https://github.com/sourcegraph/sourcegraph/issues/16030) when the bulk of the graph can be omitted.

Notes

We will need to update the integration tests to deal with this new heuristic. The existing ones are broken because we do not upload indexes roughly in commit order (which should always occur in practice except for test uploads).