Publish block before constructing blob sidecars

[StefanBratanov]

In our current implementation, we wait for creating blob sidecars (inclusion proofs etc) before publishing both the block and the blob sidecars at the same time. It would make more sense to publish the block immediately before waiting for the creation of the blob sidecars. This way, nodes can take advantage of engine_getBlobsV1 more efficiently.

Inspired by https://x.com/jimmygchen/status/1843441689622708245