Add SambaNova Support

[jhpiedrahitao]

SambaNova's SambaNovaCloud offers fast inference for multiple open-source models at full precision artificial analysis providers leaderboards

[jhpiedrahitao]

adding support in https://github.com/pydantic/pydantic-ai/pull/215

[therealjkvalentine]

Would love to see this working in pydantic, Sambanova is the only provider with a performant free tier offering Llama 405B! Very important to those of us building open-source first AI applications and/or concerned about ability to deploy on-prem e.g. https://github.com/OpenBB-finance

[samuelcolvin]

I've written up #239 with proposed rules for when to add new models, feedback welcome.

[samuelcolvin]

I've decided to adopt the rules set out in #239, so we won't be able to accept a SambaNova model at this time.

Sorry to disappoint.