Flag to try syncing blobs/columns beyond DA window

[michaelsproul]

Apparently Nimbus is able to sync a blob archive node from the P2P network, by just requesting expired blobs from peers.

We should try adding a flag to Lighthouse to attempt this. It might be an easier way for users to sync blob archive nodes (from other blob archive nodes) compared to manually importing snapshots, which is our current strategy in:

• Import expired blobs #5391