feat: return # of messages prioritized in the queue when calling mess…

…age retry endpoint (#5132)

### Description

Add a mpsc channel between relayer and message retry handler, so message
retry handler knows the retry results from the relayer.

`POST /message_retry` endpoint now returns a JSON with details on the
retry request:

```rust
#[derive(Clone, Debug, Deserialize, Serialize)]
pub struct MessageRetryResponse {
    /// ID of the retry request
    pub uuid: String,
    /// how many pending operations were processed
    pub processed: usize,
    /// how many of the pending operations matched the retry request pattern
    pub matched: u64,
}
```

#### New changes
 - use less memory by dropping uuid for some responses
 - changed channel size to 3 * number of destination chains
   - before it was just number of origin chains
- this should prevent `Sender`s from being blocked when calling `send()`
- added unittests to test `process_retry_requests` to ensure messages
are being matched properly against `MatchingList`
- use Arc for message retry requests so we don't need to clone the
entire struct
 - add constant `SUBMITTER_QUEUE_COUNT = 3`

### Drive-by changes

<!--
Are there any minor or drive-by changes also included?
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### Related issues

Fixes #4059

### Backward compatibility

<!--
Are these changes backward compatible? Are there any infrastructure
implications, e.g. changes that would prohibit deploying older commits
using this infra tooling?

Yes/No
-->

### Testing

Updated unit tests to return a response so the handler is not blocked

---------

Co-authored-by: Paul Balaji <[email protected]>

rust/main/Cargo.toml

@@ -154,6 +154,7 @@ typetag = "0.2"
 uint = "0.9.5"
 ureq = { version = "2.4", default-features = false }
 url = "2.3"
+uuid = { version = "1.12.0", features = ["v4"] }
 walkdir = "2"
 warp = "0.3"
 which = "4.3"

rust/main/agents/relayer/Cargo.toml

@@ -44,6 +44,7 @@ tokio-metrics.workspace = true
 tracing-futures.workspace = true
 tracing.workspace = true
 typetag.workspace = true
+uuid.workspace = true
 
 hyperlane-core = { path = "../../hyperlane-core", features = [
     "agent",
@@ -53,6 +54,7 @@ hyperlane-base = { path = "../../hyperlane-base", features = ["test-utils"] }
 hyperlane-ethereum = { path = "../../chains/hyperlane-ethereum" }
 
 [dev-dependencies]
+axum = { workspace = true, features = ["macros"] }
 once_cell.workspace = true
 mockall.workspace = true
 tokio-test.workspace = true

rust/main/agents/relayer/src/lib.rs

@@ -3,8 +3,9 @@ mod msg;
 mod processor;
 mod prover;
 mod relayer;
-mod server;
 mod settings;
 
+pub mod server;
+
 pub use msg::GAS_EXPENDITURE_LOG_MESSAGE;
 pub use relayer::*;