Improve the format of --debug logs

[Wwwsylvia]

As per the ORAS diagnose experience proposal, we should improve the format of the --debug logs as below:

oras/docs/proposals/diagnose-experience.md

Lines 75 to 79 in 5280c67

	- Add two empty lines as the separator between each request and response for readability.
	- Add timestamp of each request and response to the beginning of each request and response.
	- Print out the response body in the debug logs if the [Content-Type](https://www.rfc-editor.org/rfc/rfc2616#section-14.17) of the HTTP response body is JSON or plain text format. ORAS SHOULD limit the size of a response body for preventing clients from overloading the registry server with massive payloads that could lead to performance issues.
	- Upon a response with failures, the [error code](https://github.com/opencontainers/distribution-spec/blob/main/spec.md#error-codes) should be included in the response body by default for diagnose purposes.
	- Considering ORAS is not a daemon service so parsing debug logs to a logging system is not a common scenario. The target users of the debug logs are normal users and ORAS developers. Thereby, the debug logs in TTY mode and non-TTY (`--no-tty`) should be consistent, except for the color. Specifically, debug logs SHOULD be colored-code in a TTY mode for better readability on terminal but keeping plain text in a non-TTY mode.