Implement `repositoriesLike` query

As part of #151, this requires we introduce the ability to list
repositories based on `LIKE` SQL syntax, and then performing the
per-repo lookups.

Right now, we're not wrapping this up with Goroutines to improve
performance, and we'll optimise it in the future if needed.

We need to make sure we look up whether `totalAdvisories`,
`totalDependencies` or `totalPolicyViolations` are found in the query
and then generate the total values as needed, as we cannot wire in the
resolver (via GQLGen) to wait until the `repositories` field has
executed.

Co-authored-by: Keith Lyall <keith.lyall@deliveroo.co.uk>