indexer ingestion: logs for local files (MystenLabs#18577)

## Description 

Chris set up a colocated FN <> indexer, adding some logs to
differentiate the read source.

## Test plan 

How did you test the new or updated feature?

---

## Release notes

Check each box that your changes affect. If none of the boxes relate to
your changes, release notes aren't required.

For each box you select, include information after the relevant heading
that describes the impact of your changes that a user might notice and
any actions they must take to implement updates.

- [ ] Protocol: 
- [ ] Nodes (Validators and Full nodes): 
- [ ] Indexer: 
- [ ] JSON-RPC: 
- [ ] GraphQL: 
- [ ] CLI: 
- [ ] Rust SDK:

crates/sui-data-ingestion-core/src/reader.rs

@@ -220,19 +220,22 @@ impl CheckpointReader {
         })
         .await?;
 
+        let mut read_source: &str = "local";
         if self.remote_store_url.is_some()
             && (checkpoints.is_empty()
                 || checkpoints[0].checkpoint_summary.sequence_number
                     > self.current_checkpoint_number)
         {
             checkpoints = self.remote_fetch();
+            read_source = "remote";
         } else {
             // cancel remote fetcher execution because local reader has made progress
             self.remote_fetcher_receiver = None;
         }
 
         info!(
-            "Reader. Current checkpoint number: {}, pruning watermark: {}, new updates: {:?}",
+            "Read from {}. Current checkpoint number: {}, pruning watermark: {}, new updates: {:?}",
+            read_source,
             self.current_checkpoint_number,
             self.last_pruned_watermark,
             checkpoints.len(),