Other sync improvements

[zilm13]

PR Description

It's made over #11158, so it should be merged first
includes:

• increased DA timeout for older slots. Older means DA requested during batchsync so it could be up to 125 slots * 128 sidecars requested simultaneously with the same 12 seconds timeout when we are on gossip. Timeout boosted with hardcoded constant 5x
• minor guards and fixes
• last second fix from BatchSync Improvements #11158 bot discovery, import completed exceptionally will stall the batch. Fixed

Fixed Issue(s)

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

Medium Risk
Changes sync import lifecycle, DAS tracker eviction, and availability timeouts—areas that affect catch-up sync and block import under Fulu, but behavior is guarded with targeted tests.

Overview
This PR hardens multi-peer batch sync and Fulu data-column availability so large catch-up imports don’t stall or fail prematurely.

Batch import: BatchSync now uses handleAsync on batch import futures and routes exceptional completion through onImportFailed, which logs, releases importing state, and treats the outcome like IMPORT_FAILED so sync can retry instead of hanging. Import pause warnings include batch slot ranges; chain-switch while an import is in flight is covered when the delayed import fails exceptionally.

DAS during sync: DataColumnSidecarAvailabilityChecker applies a 5× slot-duration timeout for blocks more than one epoch behind the current slot (batch sync can pull ~125 slots at once). DasSamplerBasicImpl only soft-evicts sampling trackers when eviction is safe (failed sampling or sampling complete and the block is already satisfied in chain/store), keeping trackers needed for pending imports.

Sidecar retrieval: SimpleSidecarRetriever skips stale matches, cancels in-flight RPC when gossip satisfies the request, and does not penalize peer scores for client-side cancellations.

SyncConfig comments clarify the recently-sampled-blocks soft limit vs the sampler hard cap.

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[rolfyone]

LGTM