feat(block-producer): instrument block building (#675)

Author: Mirko-von-Leipzig

CHANGELOG.md

@@ -10,6 +10,7 @@
 
 - Add an optional open-telemetry trace exporter (#659).
 - Support tracing across gRPC boundaries using remote tracing context (#669).
+- Instrument the block-producer's block building process (#676).
 
 ### Changes
 

Cargo.lock

@@ -19,6 +19,7 @@ tracing-forest = ["miden-node-utils/tracing-forest"]
 
 [dependencies]
 async-trait           = { version = "0.1" }
+futures               = { version = "0.3" }
 itertools             = { workspace = true }
 miden-lib             = { workspace = true }
 miden-node-proto      = { workspace = true }