Per dependency bump schedule

I'm not sure if there is already an open issue/backlog item for this, but it would be nice to be able to set bump schedules on a per-dependency basis.

For example, I typically want daily updates to my repositories so I can get the latest packages asap, except there are a few dependencies that release daily that I don't want to have to review and merge every day. For these few dependencies (usually AWS packages), I would want them to be bumped weekly or even monthly.

Right now I have this repository set to bump weekly because of those frequently updated packages, so I get a big dump of everything on Mondays. It would be nice to change it to daily for all packages except the frequently updated ones.

Thanks for all your work on dependabot!

The issue names no files, tests, or entry points. Start by locating the current repository-wide bump-schedule configuration and dependency selection logic; done should allow named dependencies to use weekly or monthly schedules while other dependencies retain the default schedule.

Written by the indexing model from the issue text.