feat(cloudslog): store httpRequest, if available

[fredrikaverpil]

Why?

There are additional fields we could put onto the error report. See
context.httpRequest part of the schema.

The request logging middleware currently only sets httpRequest on the record
after the handler returns (for access logging). This means errors logged
during request handling never have httpRequest available for error reports.

What?

• Add a dedicated context key (cloudslog.WithHTTPRequest) to store a partial
  httpRequest on the context before request handling begins.
• The error reporting handler reads from this context key to include
  httpRequest in the error report's context group.
• The middleware (cloudrequestlog) sets the partial httpRequest on the
  context in all server-side entry points (gRPC unary, gRPC stream, HTTP).
• The access log continues to build its own full httpRequest (with status,
  latency, response size) as a record attribute after the handler returns —
  no duplication or interference.

Notes

cc @ngalaiko — addressed your feedback
about the timing issue by using a context-based approach.

[ngalaiko]

I think that would be nice to have, and I have tried it in my pr. One problem though: errors tend to happen during an http call. and cloudrequestlog will only set httpRequest when that is finished, for access logging

So to properly fix this, you should make sure that some of the httpRequest data (url, etc.) is set before request is handeled, and the rest (status code, duration) is added after.

http middleware: https://github.com/einride/cloudrunner-go/blob/master/cloudrequestlog/middleware.go#L189-L223