Follow up on Blob encoding alloy issues

[segfault-magnet]

alloy-rs/alloy#1388

We've copied some of the faulty code (PartialSidecar) from alloy into the committer and fixed it.

Once alloy fixes and releases make sure to implement our own coder (fine to just copy the simple coder and remove the limit) that will not limit the amount of data encoded to 6 blobs.