feat(metrics): add stateful Foldspace transport

Author: aqian01

.cargo/config.toml

@@ -6,3 +6,6 @@ rustflags = ["--cfg", "tokio_unstable", "-C", "target-feature=+crt-static"]
 
 [env]
 JEMALLOC_SYS_WITH_MALLOC_CONF = "abort_conf:true,max_background_threads:1,narenas:1,tcache:false,thp:never,oversize_threshold:32768,dirty_decay_ms:1000,muzzy_decay_ms:0"
+
+[registries]
+datadog-rust-testing = { index = "sparse+https://depot-read-api-rust.us1.ddbuild.io/datadog/rust-testing/" }