feat: Cache model and engine downloads so users can restart download

[freelerobot]

Problem:

1. cortex run trt/onnx model
2. wait for download
3. 10 minutes in, something might happen, internet drops/windows goes to sleep, etc.
4. Lose entire download progress.
5. Sadness

Happened for me 2/3 times for larger model folders

Suggested solution

• cache downloads, host a mirror, open to better suggestions

[freelerobot]

Related issues:

• bug: Model corruption during download leads to loading failure #1139
• bug: cortex pull from hf times out #1017
• bug: Download models/engine failed cause api server stop #1010
• feat: Add pause functionality to model downloader jan#3519

Related discussion:
#1129

[dan-menlo]

Linking this to main issue #1077

[hiento09]

Hien will help to add checksum and version to cortex.tensorrtllm, cortex.llamacpp, cortex.onnx

[namchuai]

proposed:
file name: version.txt
content: yaml compatible

name: full_name (vulkan/os/arch for us to troubleshoot issue in the future)
version: x.y.z
description: (optional)

[hiento09]

For checksum.yml file, use format similar to Jan app
Content: yaml compatible

version: 0.5.3
files:
  - url: jan-mac-arm64-0.5.3.zip
    sha512: >-
      GE3eaRoDi/fuqzdC0SQBvKvwjPGVPPBeulCo4JkjZuZ+0FLx0AiT/LgoUIMiOLh5LSR0Q73emkMsSBIcQco4bg==
  - url: jan-mac-arm64-0.5.3.dmg
    sha512: >-
      bpB8x0UajDWvshJ37NmuQVLl9MqUd3J/7yydKWtpuEJBsu2TxXB8qJSta1mvxXGBke7SS13V2y3syP/qerHvoA==
  - url: jan-mac-x64-0.5.3.zip
    sha512: >-
      oX0mTvuqshXoy3TEVmw+JQGJaeJK//42j+UL6VTJus/637LeLzf3m/8TtIZMe7Ac6k5zpTox8bWqjIz5mKp6Bg==
  - url: jan-mac-x64-0.5.3.dmg
    sha512: >-
      Hd9SPyJM9TL2CVG0Is4lQzCSAXcn4WhVmra6hSBx0PgVN9L6utdc+yiYnhtd1L6x9BR1mwlZ3UCSJ8Ffr1wwJA==