Improve error types for envelopes (#9414)

N/A


  Currently, we have `EnvelopeError` having a `ImportError` wrapping a `BlockError`. I feel this is extremely unintuitive because most of the envelope processing functions can simply return an `EnvelopeError` that makes sense in the function's context. It revealed further ugliness when implementing range sync in #9362

This PR does 2 main things:
1. Removes `ImportError(BlockError)` variant
2. Adds `EnvelopeError(EnvelopeError)` variant to a `BlockError`.

I feel this is more natural as there can be envelope errors when we try importing a Block but envelope errors can be contained to just envelope related errors.

The main blocker to doing this was `PayloadVerificationHandle` returning a `BlockError`. It uses a very small subset of `BlockError` which I extracted to its own error type which can be converted into both a BlockError and EnvelopeError.

This allows us to keep most of the pure envelope processing functions to just return EnvelopeErrors while we convert it to a `BlockError` only in import paths where we need to return a consolidated `BlockError`.


Co-Authored-By: Pawan Dhananjay <pawandhananjay@gmail.com>

beacon_node/beacon_chain/src/beacon_chain.rs

@@ -4104,6 +4104,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
                 publish_fn()?;
                 self.import_available_execution_payload_envelope(available_envelope)
                     .await
+                    .map_err(Into::into)
             }
             PayloadAvailability::MissingComponents(block_root) => Ok(
                 AvailabilityProcessingStatus::MissingComponents(slot, block_root),