Pass blobs into ValidatorStore::sign_block (#7497)

While the Lighthouse implementation of the `ValidatorStore` does not really care about blobs, Anchor needs to be able to return different blobs from `sign_blocks` than what was passed into it, in case it decides to sign another Anchor node's block. Only passing the unsigned block into `sign_block` and only returning a signed block from it (without any blobs and proofs) was an oversight in #6705.


  - Replace `validator_store::{Uns,S}ignedBlock` with `validator_store::block_service::{Uns,S}ignedBlock`, as we need all data in there.
- In `lighthouse_validator_store`, just add the received blobs back to the signed block after signing it.

Cargo.lock

@@ -9804,6 +9804,7 @@ dependencies = [
 name = "validator_store"
 version = "0.1.0"
 dependencies = [
+ "eth2",
  "slashing_protection",
  "types",
 ]
@@ -10059,6 +10060,7 @@ dependencies = [
  "account_utils",
  "async-channel 1.9.0",
  "environment",
+ "eth2",
  "eth2_keystore",
  "eth2_network_config",
  "futures",