maybeRebroadcastQueries on queries and direct cache writes

[micimize]

Right now cache.writeQuery flags the cache for rebroadcast, but the only time maybeRebroadcastQueries is in mutate

Also, this docstring is wrong, I believe because I didn't want to needlessly rebroadcast. Need to re-investigate:
https://github.com/zino-app/graphql-flutter/blob/7192c1669c7dbecff0bbcd0665522c5b41207ab2/packages/graphql/lib/src/core/query_manager.dart#L282

We should either maybeRebroadcastQueries at the end of every query and cache write, or it should be somehow configurable via a rebroadcastPolicy

Consolidating #647 and #587 here

[micimize]

As part of this, we should have the direct cache access methods accessible on the client with rebroadcasting capacity. Thus consolidating that part of #176 here as well

[micimize]

I was pretty wrong here – maybeRebroadcastQueries was already called every time a result was added. Added clearer docstrings to avoid making this mistake again

4.0.0-alpha.7 adds cache access methods to the client that handle rebroadcasting, closing this entirely.