[Feature] Support Lightllm api

[helloyongyang]

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Motivation

To support lightllm api.
lightllm: https://github.com/ModelTC/lightllm

Modification

Add LightllmApi in lightllm_api.py.
Add a config file named eval_lightllm.py.

BC-breaking (Optional)

Do not introduce changes that break the backward compatibility of the downstream repositories.

Use cases (Optional)

`
git clone https://github.com/ModelTC/lightllm.git

cd lightllm

python -m lightllm.server.api_server --model_dir /path/llama-7b --tp 1 --max_total_token_num 121060 --tokenizer_mode auto

cd opencompass
python run.py configs/eval_lightllm.py
`

Checklist

Before PR:

• Pre-commit or other linting tools are used to fix the potential lint issues.
• Bug fixes are fully covered by unit tests, the case that causes the bug should be added in the unit tests.
• The modification is covered by complete unit tests. If not, please add more unit test to ensure the correctness.
• The documentation has been modified accordingly, like docstring or example tutorials.

After PR:

• If the modification has potential influence on downstream or other related projects, this PR should be tested with those projects.
• CLA has been signed and all committers have signed the CLA in this PR.