Record element start events and report them when the event_count feature is enabled.

Cargo.toml

@@ -59,6 +59,7 @@ default = []
 compare = ["tokio/process", "tokio/macros"]
 foreign_document_test = ["compare", "dep:futures", "tokio/sync", "dep:walkdir", "tokio/process"]
 tracing = ["dep:opentelemetry", "dep:opentelemetry-otlp", "dep:opentelemetry-semantic-conventions", "dep:tokio", "dep:tracing", "dep:tracing-opentelemetry", "dep:tracing-subscriber"]
+event_count = []
 
 # Optimized build for any sort of release.
 [profile.release-lto]