dd-trace: Improper parsing of W3C baggage headers may lead to DoS

dd-trace is the Datadog APM client for Node.js. Prior to 5.100.0, W3C baggage propagation in packages/dd-trace/src/baggage.js and packages/dd-trace/src/opentracing/propagation/text_map.js parsed incoming baggage HTTP headers without enforcing DD_TRACE_BAGGAGE_MAX_ITEMS or DD_TRACE_BAGGAGE_MAX_BYTES on extraction. A remote, unauthenticated attacker can send a request whose baggage header contains an arbitrarily large number of comma-separated key-value pairs, or a single very large value, causing unbounded CPU and memory consumption and enabling a remote denial of service against any HTTP service with baggage propagation enabled. This issue is fixed in version 5.100.0.