improve readability of registry debug logs

[qweeah]

trace package provides http level debug logging for registry-related commands. Since the outgoing requests and incoming response can be processed concurrently, logs in different may intersect between different roundtrip calls.

To make concurrent logs more readable:

1. Logs for each request/response should be taken atomically. Taking request logging as an example, below logs should be taken in one Logrus call:

oras/internal/trace/transport.go

Lines 40 to 43 in d93544d

	e.Debugf("> Request URL: %q", req.URL)
	e.Debugf("> Request method: %q", req.Method)
	e.Debugf("> Request headers:")
	logHeader(req.Header, e)

2. Add a counter for each request/response so a roundtrip pair can be correlated like below:

Request #1
> URL: "http://localhost:5000/v2/command/images/manifests/multi"
> Method: "GET"
> Headers:
   "Accept": "application/vnd.docker.distribution.manifest.v2+json, application/vnd.docker.distribution.manifest.list.v2+json, application/vnd.oci.image.manifest.v1+json, application/vnd.oci.image.index.v1+json, application/vnd.oci.artifact.manifest.v1+json"
   "User-Agent": "oras/1.0.0-rc.1"

Request #2
> URL: "http://localhost:5000/v2/command/images/manifests/multi"
> Method: "GET"
> Headers:
   "Accept": "application/vnd.docker.distribution.manifest.v2+json, application/vnd.docker.distribution.manifest.list.v2+json, application/vnd.oci.image.manifest.v1+json, application/vnd.oci.image.index.v1+json, application/vnd.oci.artifact.manifest.v1+json"
   "Authorization": "*****"
   "User-Agent": "oras/1.0.0-rc.1"

Response #2
< Status: "200 OK"
< Headers:
   "Content-Length": "706"
   "Content-Type": "application/vnd.oci.image.index.v1+json"
   "Docker-Content-Digest": "sha256:e2bfc9cc6a84ec2d7365b5a28c6bc5806b7fa581c9ad7883be955a64e3cc034f"
   "Docker-Distribution-Api-Version": "registry/2.0"
   "Etag": "\"sha256:e2bfc9cc6a84ec2d7365b5a28c6bc5806b7fa581c9ad7883be955a64e3cc034f\""
   "X-Content-Type-Options": "nosniff"
   "Date": "Thu, 02 Mar 2023 15:14:31 GMT"

Response #1
< Status: "401 Unauthorized"
< Headers:
   "Content-Type": "application/json"
   "Docker-Distribution-Api-Version": "registry/2.0"
   "Www-Authenticate": "Basic realm=\"test-basic\""
   "X-Content-Type-Options": "nosniff"
   "Date": "Thu, 02 Mar 2023 15:14:31 GMT"
   "Content-Length": "157"
...

[wangxiaoxuan273]

I would like to work on this item.