Support Trace Context HTTP headers

[lidel]

Ref.

• https://github.com/w3c/trace-context#trace-context-specification
• https://w3c.github.io/trace-context/
  • https://w3c.github.io/trace-context/#processing-model
• Support propagation of trace context headers in http gateway ipfs/kubo#9168 + Emit traceparent header in gateway responses and add sharness test ipfs/kubo#9180

Quick thoughts:

• Whatever we establish here, others in IPFS Ecosystem will see, and assume this is "standard best practice" – we should plan for long term
• This should be turn-key solution for everyone running boxo/gateway, not just bifrost-gateway
• bifrost-gateway should ensure tracing info is always present
  • If it is missing in request, bifrost-gateway would create one. (spec)
  • If it is present in request, we update ids in the chain.
    • For Rhea, we will be creating trace parent on LBs (slack thread), but if there is no load balancer in front of bifrost-gateway, then it should initialize trace chain.

### Tasks
- [x] https://github.com/ipfs/bifrost-gateway/pull/74
- [ ]  https://github.com/filecoin-saturn/caboose/pull/87
- [ ] https://github.com/filecoin-saturn/L1-node/issues/337

[lidel]

@hacdias some prior art in ipfs/kubo#9168 + ipfs/kubo#9180, any chance to upstream that to boxo/gateway? Might be less work than we've anticipated 🤞

[lidel]

wip in #74 (review), quick demo by @hacdias

I'm using Kubo @ ipfs/kubo#9801 for testing.

Connected traces of Bifrost Gateway proxying requests to Kubo (PROXY_GATEWAY_URL):

Connected traces of Bifrost Gateway proxying IPNS records to Kubo (KUBO_RPC_URL):

STRN_ORCHESTRATOR_URL should work since we wrap the caboose transport with otelhttp and caboose already uses the request with context:

https://github.com/filecoin-saturn/caboose/blob/34e6ab0f0e60ed6bef02b06242573aa5ab06bd37/fetcher.go#L215-L219