Add GigaChat API

[seldereyy]

This PR is an update for #1996 .

This PR adds the GigaChat models API. GigaChat models are proprietary, so the log-likelihood methods are not available.
Two authorization methods are available: using an access token or API credentials.
If you have an access token, set the GIGACHAT_CREDENTIALS environmental variable with its value and use base_url for your token.
For authorization through API credentials, set the following environmental variables:

• GIGACHAT_RQUID - Unique identification request. Complies with the uuid4 format. The value must match the regular expression ([0-9a-fA-F-]{36}).
• GIGACHAT_TOKEN - Client Secret. Credential for the GigaChat API.
• GIGACHAT_SCOPE - Type of your API. Possible values: ["GIGACHAT_API_PERS", "GIGACHAT_API_B2B", "GIGACHAT_API_CORP"]. The default value is "GIGACHAT_API_PERS".

You also need to set base_url and auth_url in the model_args parameter.

• base_url - URL for chat completion.
• auth_url - URL for obtaining the authorization token.

Choose a model from the available options: GigaChat, GigaChat-Plus, GigaChat-Pro, GigaChat-Max.

Here is a usage example for the GSM8K benchmark with API authorization:

export GIGACHAT_TOKEN="XXX"
export GIGACHAT_RQUID="XXX"

lm_eval --model gigachat_llms \
    --model_args model="MODEL_NAME",base_url="BASE_URL",auth_url="AUTH_URL" \
    --tasks gsm8k \
    --device cpu \
    --write_out \
    --apply_chat_template \
    --log_samples \
    --output_path 'OUTPUT_PATH'

Example for access_token authorization:

export GIGACHAT_CREDENTIALS="XXX"

lm_eval --model gigachat_llms \
    --model_args model="MODEL_NAME",base_url="BASE_URL" \
    --tasks gsm8k \
    --device cpu \
    --write_out \
    --apply_chat_template \
    --log_samples \
    --output_path 'OUTPUT_PATH'

Some technical details:

• We use the property decorator (not cached_property) for the api_key and header methods because we need to issue a new access_token every 30 minutes.
• The GigaChat API does not have a "do sample" option. We removed it and use the top_p parameter instead.