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

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'`.