cloudflare-integration-tests: port tracing suites to span streaming #24147

Follow the porting recipe in the parent issue. Blocked on the runner helper sub-issue.

Suites

• tracing/propagation/* (12 pinned files, the biggest block)
• tracing/opentelemetry-tracer/* (4 pinned files)
• Durable Objects: tracing/durableobject, durableobject-spans, durableobject-sql, durableobject-sync-kv, durableobject-rpc-private-fields, durableobject-alarm-links, durableobject-alarm-links-sync
• gen_ai: tracing/openai, tracing/anthropic-ai, tracing/google-genai, tracing/langchain, tracing/langgraph, tracing/workers-ai
• Rest: tracing/d1, tracing/headers, tracing/dsc-url-source, tracing/instrument-fetcher, tracing/scheduled, tracing/workflow

Twins and env gates

• Fold tracing/ignoreSpans-streamed back into its static original.
• tracing/d1 uses an env-gated STREAMED switch. Drop the switch and keep 'stream'.