Serve finalized data columns by root via req/resp

[philknows]

Problem description

Based on Berlinterop, there was an idea to serve this for helping with sync issues especially during turbulent network conditions

Solution description

Should not be difficult to implement

Additional context

No response

[nflaig]

we already have the database indices for this and can serve those blocks via beacon-api

[nflaig]

Related spec ethereum/consensus-specs#4394

[nflaig]

For reference, we already support serving finalized blocks by root

lodestar/packages/beacon-node/src/network/reqresp/handlers/beaconBlocksByRoot.ts

Lines 19 to 45 in 9ed8317

	// finalized block has summary in forkchoice but it stays in blockArchive db
	if (summary) {
	blockBytes = await db.block.getBinary(root);
	}
	let slot: Slot | undefined = undefined;
	if (!blockBytes) {
	const blockEntry = await db.blockArchive.getBinaryEntryByRoot(root);
	if (blockEntry) {
	slot = blockEntry.key;
	blockBytes = blockEntry.value;
	}
	}
	if (blockBytes) {
	if (slot === undefined) {
	const slotFromBytes = getSlotFromSignedBeaconBlockSerialized(blockBytes);
	if (slotFromBytes === null) {
	throw Error(`Invalid block bytes for block root ${toRootHex(root)}`);
	}
	slot = slotFromBytes;
	}
	yield {
	data: blockBytes,
	boundary: chain.config.getForkBoundaryAtEpoch(computeEpochAtSlot(slot)),
	};

Just need to do the same for data columns #8250