Add detailed token stats for every API call

[mikhailsal]

Currently, each API request in the statistics only shows the price. However, many models are now free or have a low cost, making these figures less informative.

I believe it would be very convenient to optimize prompts and requests if not only the price but also the number of tokens for each request were visible. The number of cached tokens would be especially valuable.

Optionally, it would also be interesting to see the speed of incoming and outgoing tokens, although this is somewhat less important.

I could potentially try to implement this improvement myself if the maintainers agree to accept this feature.

[mikhailsal]

Later I realized that I could have created an issue right away, which I did - #7740
But I can no longer delete this topic.