[Feature] remove dependency on enable_mm and refine multimodal's code (#3014)

* remove dependency on enable_mm

* fix codestyle check error

* fix codestyle check error

* update docs

* resolve conflicts on model config

* fix unit test error

* fix code style check error

---------

Co-authored-by: shige <1021937542@qq.com>
Co-authored-by: Jiang-Jia-Jun <163579578+Jiang-Jia-Jun@users.noreply.github.com>

docs/zh/get_started/ernie-4.5-vl.md

@@ -31,7 +31,6 @@ python -m fastdeploy.entrypoints.openai.api_server \
        --quantization wint4 \
        --max-model-len 32768 \
        --max-num-seqs 32 \
-       --enable-mm \
        --mm-processor-kwargs '{"video_max_frames": 30}' \
        --limit-mm-per-prompt '{"image": 10, "video": 3}' \
        --reasoning-parser ernie-45-vl