Add support for Vercel as a language model provider (#33292)

Vercel v0 is an OpenAI-compatible model, so this is mostly a dupe of the
OpenAI provider files with some adaptations for v0, including going
ahead and using the custom endpoint for the API URL field.

Release Notes:

- Added support for Vercel as a language model provider.

crates/icons/src/icons.rs

@@ -19,6 +19,7 @@ pub enum IconName {
     AiOllama,
     AiOpenAi,
     AiOpenRouter,
+    AiVZero,
     AiZed,
     ArrowCircle,
     ArrowDown,