Support pagination in GraphQL requests

A new record number of breakouts were proposed for TPAC 2024. That's great but a hidden assumption in the code is that the number of open issues will never exceed 100 because that's the limit in GraphQL queries. If we need to go beyond 100, we'll have to support pagination, see [Using pagination in the GraphQL API](https://docs.github.com/en/graphql/guides/using-pagination-in-the-graphql-api)