fix deadlock in console caused by SimpleSpanProcessor (#60)

* fix deadlock in console caused by `SimpleSpanProcessor`

* accept some test diffs, note problem

* always produce a span, even if never entered

Author: davidhewitt

Cargo.toml

@@ -36,6 +36,8 @@ chrono = "0.4.39"
 regex = "1.11.1"
 
 [dev-dependencies]
+async-trait = "0.1.88"
+futures = { version = "0.3.31", features = ["futures-executor"] }
 insta = "1.42.1"
 opentelemetry_sdk = { version = "0.30", default-features = false, features = ["testing"] }
 regex = "1.11.1"