feat: Cortex multiple engines onboarding

[Van-QA]

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[louis-jan]

Update:

• As a new user, I can list all available engines with cortex engines list

• As a new user, I can install any engine with the engine name: cortex engines init cortex.tensorrt-llm

• When pulling or starting any model, if the engine is not initialized, it will be installed beforehand:

cc @gabrielle-ong @Van-QA