Persist and prune blob data correctly

[txhsl]

Rationale

Ref #499 (comment), the current Geth implementation only handles the metadata of blob transaction and leaves the persistence of blob data to consensus layer.

The lifecycle of EIP-4844 should be like:

1. Blob transactions are sent to EL blob pool;
2. Blob metadata and sidecars are committed to CL;
3. CL confirms the blob transaction and store the data;
4. EL deletes the temporary storage for blob transactions after CL finalized (about 12.8 mins, 2 epochs of 32 blocks);
5. CL prunes the file storage for blob data after expiration (about 18.2 days, 4096 epochs of 32 blocks).

It is supposed that the CL maintains the final storage. Since we don't have a corresponding consensus layer (it's a separated program definition), our client only packs the blob transactions into blocks but evicts the blob data after a short period of time (the billy database is not designed for long-term storage).

Implementation

Relate to #233, #496 and #507.

The blob transaction is handled, yes. But we need to store the blob data as well, if we want to support the functionality of EIP-4844 correctly.

[txhsl]

A practical choice from BSC, bnb-chain/bsc#2279. Their design can be referred https://forum.bnbchain.org/t/design-eip-4844-on-bsc/2621.

But at least we need an independent protocol to transfer blob optionally, putting them inside ETH protocol betrays the proposal of blob data separation.

And it seems not good enough to store the blobs in database, because they are 128 KB each.