Add request/response debug logging

[parthea]

This PR was built on top of #2265

Example debug logs

{"timestamp": "2024-11-29 12:30:05,731", "severity": "DEBUG", "name": "google.showcase_v1beta1.services.echo.client", "message": "Created client `google.showcase_v1beta1.EchoClient`.", "serviceName": "google.showcase.v1beta1.Echo", "universeDomain": "googleapis.com", "credentialType": "google.oauth2.credentials.Credentials", "credentialInfo": {"credential_source": "REDACTED", "credential_type": "user credentials"}}

{"timestamp": "2024-11-29 12:30:07,220", "severity": "DEBUG", "name": "google.showcase_v1beta1.services.echo.client", "message": "Sending request via google.showcase_v1beta1.EchoClient.echo", "rpcName": "Echo", "serviceName": "google.showcase.v1beta1.Echo", "request": "{\n  \"content\": \"The hail in Wales falls mainly on the snails.\",\n  \"requestId\": \"some_value\",\n  \"otherRequestId\": \"\",\n  \"severity\": 0,\n  \"header\": \"\",\n  \"otherHeader\": \"\"\n}", "retryAttempt": 1, "metadata": "{'some-key-bin': b'some_value', 'x-goog-api-version': 'v1_20240408'}"}