feat(github): GraphQL cache for datasources (#19059)

...ithub/graphql/cache-strategies/abstract-cache-strategy.ts

...ub/graphql/cache-strategies/memory-cache-strategy.spec.ts

.../github/graphql/cache-strategies/memory-cache-strategy.ts

...b/graphql/cache-strategies/package-cache-strategy.spec.ts

...github/graphql/cache-strategies/package-cache-strategy.ts

lib/util/github/graphql/datasource-fetcher.spec.ts

lib/util/github/graphql/datasource-fetcher.ts

lib/util/github/graphql/readme.md

lib/util/github/graphql/types.ts

lib/util/github/graphql/util.spec.ts

lib/util/github/graphql/util.ts