Add conversion tests for pending blobs. (#3124)

## Motivation

In #3121 I added gRPC message types but forgot to write conversion unit
tests.

## Proposal

Add the missing tests.

## Test Plan

This!

## Release Plan

- Nothing to do / These changes follow the usual release cycle.

## Links

- PR with missing tests: #3121
- [reviewer
checklist](https://github.com/linera-io/linera-protocol/blob/main/CONTRIBUTING.md#reviewer-checklist)

Author: afck

linera-rpc/src/grpc/conversions.rs

@@ -951,7 +951,7 @@ pub mod tests {
 
     use linera_base::{
         crypto::{BcsSignable, CryptoHash, KeyPair},
-        data_types::{Amount, Round, Timestamp},
+        data_types::{Amount, Blob, Round, Timestamp},
     };
     use linera_chain::{
         data_types::{Block, BlockExecutionOutcome},
@@ -1085,6 +1085,20 @@ pub mod tests {
         round_trip_check::<_, api::ChainInfoQuery>(chain_info_query_some);
     }
 
+    #[test]
+    pub fn test_pending_blob_request() {
+        let chain_id = ChainId::root(2);
+        let blob_id = Blob::new(BlobContent::new_data(*b"foo")).id();
+        let pending_blob_request = (chain_id, blob_id);
+        round_trip_check::<_, api::PendingBlobRequest>(pending_blob_request);
+    }
+
+    #[test]
+    pub fn test_pending_blob_result() {
+        let blob = BlobContent::new_data(*b"foo");
+        round_trip_check::<_, api::PendingBlobResult>(blob);
+    }
+
     #[test]
     pub fn test_lite_certificate() {
         let key_pair = KeyPair::generate();