[WIP] DAS friendly lookup sync

[dapplion]

Combines two to simplify block lookup code:

1. Remove child_components, cache them inside the existing request State enum

Add a new intermediary state where a single block request state can be paused if its parent is unknown, and resumed once the parent is processed.

2. Re-use single lookups to do parent requests

Parent lookups are cached separately to bound:

• max concurrent parent lookup branches
• max depth of parent lookup branches

We can iterate the existing single block lookups and enforce those conditions

Point 1. unlocks this simplification, adding some more logic in the known parent path to:

• Filter failed chains
• Enforce the parent lookup branches bounds
• Re-process paused lookups when their parent is known

We lose a slight optimization of processing the pending chain of unknown parent blocks as a batch, but this shouldn't make a big different IMO, but please tell me otherwise.

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The simplification is quite big, preview this over to @realbigsean who really dig with it.

Next steps

• Enforce the parent lookup branches bounds
• Better name for the Action enum?
• Update tests

[dapplion]

Implemented in

• Block lookup sync technical debt #5549