[epic] imperatively loaded resolvers

[rbalicki2]

• useImperativeReference lets you imperatively load a new entrypoint (its naming sucks!)
• We should be able to do that for a client field, e.g.

field Query.foo {
  bar @loadedImperatively #or  
  bar | loadedImperatively
}

Not really sure yet about the syntax.

• This should be read out as an object with type { kind: 'NotLoaded', load: () => void } | { kind: 'Loading' } | { kind: 'Loaded', data, dispose: () => void }
• Or something. I'm not really sure.

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Open questions

• How does this relate to refetching with different variables? Those should probably have similar read out types
• Likewise, pagination should probably be similar