axum-tracing-opentelemetry-v0.21.0

Fixed

• 🐛 workaround for a delay, batch,... behavior in otlp exporter and test with fake-opentelemetry-collector (closed too early)
• 🐛 fix build of contributions (upgrade of opentelemetry, fake collector for logs,...)
• 🐛 Re-export tracing_level_info feature from axum to sdk (#147)

Changed

• 💄 update deprecated syntax "default_features" in Cargo.toml
• ⬆️ upgrade to rstest 0.22