[Config] Enhance ModelRecord

[CharlieFRuan]

There are three changes to ModelRecord this PR brings:

1. Update model ids to match HF repo name

We rename modelId in webllm.prebuiltAppConfig to be the exact same as the HF repo name. For most models, that means we simply append -MLC to the modelId. For the low-context version of the model, we would have {HF-repo}-1k, suggesting 1k context length.

As a result, we rename Phi2 and phi1.5 models since their modelId did not match with the repo name

• Phi2-q4f32_1 → phi-2-q4f32_1-MLC
• Phi1.5-q4f16_1 → phi-1_5-q4f16_1-MLC

2. Rename model_url and model_lib_url to model and model_lib

To better match with other platforms of MLC-LLM (e.g. iOS, Android), we rename the ModelRecord fields.

3. Remove resolve/main from model URL

Instead of "https://huggingface.co/mlc-ai/Llama-3-8B-Instruct-q4f16_1-MLC/resolve/main/", we now make it "https://huggingface.co/mlc-ai/Llama-3-8B-Instruct-q4f16_1-MLC/"; note the trailing / will be appended by us if it is not there.

Example

As an example, we would have:

    {
      model: "https://huggingface.co/mlc-ai/Llama-3-8B-Instruct-q4f16_1-MLC",
      model_id: "Llama-3-8B-Instruct-q4f16_1-MLC",
      model_lib: "path/to/Llama-3-8B-Instruct-q4f16_1-ctx1k_cs1k-webgpu.wasm",
    },

instead of

    {
      model_url: "https://huggingface.co/mlc-ai/Llama-3-8B-Instruct-q4f16_1-MLC/resolve/main/",
      model_id: "Llama-3-8B-Instruct-q4f16_1",
      model_lib_url: "path/to/Llama-3-8B-Instruct-q4f16_1-ctx4k_cs1k-webgpu.wasm",
    },