Return HTTP 404 rather than 405 (sigp#3836)

Issue sigp#3112

Add `Filter::recover` to the GET chain to handle rejections specifically as 404 NOT FOUND

Making a request to `http://localhost:5052/not_real` now returns the following:

```
{
    "code": 404,
    "message": "NOT_FOUND",
    "stacktraces": []
}
```

Co-authored-by: Paul Hauner <paul@paulhauner.com>

beacon_node/http_api/src/lib.rs

@@ -3491,7 +3491,8 @@ pub fn serve<T: BeaconChainTypes>(
                 .or(get_lighthouse_block_packing_efficiency.boxed())
                 .or(get_lighthouse_merge_readiness.boxed())
                 .or(get_lighthouse_blobs_sidecars.boxed())
-                .or(get_events.boxed()),
+                .or(get_events.boxed())
+                .recover(warp_utils::reject::handle_rejection),
         )
         .boxed()
         .or(warp::post().and(
@@ -3516,7 +3517,8 @@ pub fn serve<T: BeaconChainTypes>(
                 .or(post_lighthouse_database_reconstruct.boxed())
                 .or(post_lighthouse_database_historical_blocks.boxed())
                 .or(post_lighthouse_block_rewards.boxed())
-                .or(post_lighthouse_ui_validator_metrics.boxed()),
+                .or(post_lighthouse_ui_validator_metrics.boxed())
+                .recover(warp_utils::reject::handle_rejection),
         ))
         .recover(warp_utils::reject::handle_rejection)
         .with(slog_logging(log.clone()))