Add Single block provider for Fulu

[gfukushima]

PR Description

This PR add a SingleBlockProviderResolver that will return recent blocks from the tracker from FULU (DASBasicSampler) or previous forks (BlockBlobSidecarsTrackersPoolImpl)

Fixed Issue(s)

Part of #10101

Documentation

• I thought about documentation and added the doc-change-required label to this PR if updates are required.

Changelog

• I thought about adding a changelog entry, and added one if I deemed necessary.

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Note

Adds a resolver to fetch recent blocks from the DAS sampler (FULU) or blob tracker, and refactors DAS sampler into an interface with a new implementation and APIs, integrating across sync, fork choice, and tests.

• Core/FULU DAS:
  • Split DasSamplerBasic into interface and new DasSamplerBasicImpl; add metrics and bounded in-memory tracking.
  • Change DataAvailabilitySampler.checkDataAvailability to accept SignedBeaconBlock; add containsBlock/getBlock to DasSamplerBasic.
  • Update DasPreSampler and DataColumnSidecarAvailabilityChecker to new API.
  • Reference tests updated to instantiate DasSamplerBasicImpl.
• Block retrieval:
  • Introduce SingleBlockProviderResolver to fetch blocks from DasSamplerBasic first, then BlockBlobSidecarsTrackersPool; wire into BeaconChainController for StorageBackedRecentChainData.
  • Add tests for resolver behavior.
• Sync/recent blocks:
  • RecentBlocksFetchService now depends on DasSamplerBasic and skips fetching when sampler already has the block; propagate via DefaultSyncServiceFactory and test fixtures.
• Wiring:
  • BeaconChainController initializes and exposes dasSamplerBasic (or NOOP pre-FULU) and passes it to sync; subscribes to slot events; integrates resolver.
  • Tests adjusted to new constructors and method signatures.

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[tbenr]

I think the direction is actually what I was having in mind. sorry for the lag