performance-metrics: Add util module with shared micro benchmark helpers

These factor out common setup and synchronization patterns used by block
layer micro benchmarks.

Signed-off-by: Anatol Belski <anbelski@linux.microsoft.com>

performance-metrics/Cargo.toml

@@ -11,6 +11,7 @@ serde = { workspace = true, features = ["derive", "rc"] }
 serde_json = { workspace = true }
 test_infra = { path = "../test_infra" }
 thiserror = { workspace = true }
+vmm-sys-util = { workspace = true }
 
 [lints]
 workspace = true