Phase-3: Add vLLM Support for Mistral-Small-3.1-24B-Instruct-2503

[nikileshx]

Ticket

Link to JIRA

Problem description

Add vLLM Support for Mistral-Small-3.1-24B-Instruct-2503

What's changed

Added vLLM support for Mistral-Small-3.1-24B-Instruct-2503 in generator_vllm

Checklist

• All post commit CI passes
• Blackhole Post commit CI with demo tests passes (if applicable)
• Model regression CI passes (if applicable)
• Device performance regression CI passes (if applicable)
• (For models and ops writers) Single-card demo tests CI passes (if applicable) See recommended dev flow.
• Galaxy quick CI passes (if applicable)
• TG demo tests, for Llama CI passes, if applicable, because of current Llama work
• (For runtime and ops writers) T3000 unit tests CI passes (if applicable, since this is run on push to main)
• (For models and ops writers) T3000 demo tests CI passes (if applicable, since this is required for release)
• (For models and ops writers) Single-card demo tests CI passes (if applicable, since this is required for release)
• New/Existing tests provide coverage for changes