llama.vim: filter server response fields

[VJHack]

As of 10940, we are now able to serialize only relavent data.

A suggestion was made here to filter out unnecessary fields in the response. This feature ensures that we are transporting the most minimal response from the server to the client.

There are two places where this change was made:

1. When we make the curl request in ring_update() to asyncronously process extra_context, we filter out all response fields since we don't take any action on the response.
2. These are the response fields we want to include when making the main fim call

'response_fields':  [ 
                     "content",
                     "timings/prompt_n", 
                     "timings/prompt_ms", 
                     "timings/prompt_per_token_ms",
                     "timings/prompt_per_second",
                     "timings/predicted_n", 
                     "timings/predicted_ms", 
                     "timings/predicted_per_token_ms",
                     "timings/predicted_per_second",
                     "truncated",
                     "tokens_cached",
                     "generation_settings/n_ctx",
                     ], 

[ggerganov]

After recent refactoring, the server no longer provides the n_ctx field in the responses. We should remove it from the llama.vim client and instead of displaying:

c: 1234 / 0 | ...

We should simply display:

c: 1234 | ...

[VJHack]

I did notice that. I removed all instances of n_ctx field and adjusted the info message accordingly as shown below.

Thank you!