feat: follow (but partially ignore) repo config

One of the original decisions made in renovate-graph was to ignore any configuration in a repository, which would surface the dependencies regardless of onboarding of Renovate, or the owners deciding which dependencies should (not) be updated.

However, this led to cases where the definition of customManagers (historically regexManagers) would be missed, leading to a number of dependencies not being picked up correctly.

We can handle this better by following the repo config, if present, but forcibly disabling the options that would disable any package lookups.

Closes #36 (closed), #37 (closed) #42 (closed).