feature: Get timing metrics

[chitralverma]

Any way to get timings for the requests with this lib? ability to get metrics like below would be great

• http_req_blocked: Time spent on DNS resolution, waiting for a connection from the pool, etc.
• http_req_connecting: Time spent establishing the TCP connection.
• http_req_tls_handshaking: Time spent performing the SSL/TLS handshake.
• http_req_sending: Time taken to send the HTTP request to the server.
• http_req_receiving: Time taken to receive the first byte of the response from the server.
• http_req_waiting: Time spent waiting for the server to start sending the response.
• http_req_duration: Total time taken from the start to the end of the request.

[spyoungtech]

This library does not provide any metrics or timings. However, there are other tools like profilers or tracing/telemetry agents that may help you achieve what you're looking for.

As it stands, this is outside of the scope of grequests so I'm going to close this issue.