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.

Cargo.lock

@@ -8985,6 +8985,7 @@ dependencies = [
  "ui",
  "ui_input",
  "util",
+ "vercel",
  "workspace-hack",
  "zed_llm_client",
 ]
@@ -17424,6 +17425,20 @@ version = "0.2.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "accd4ea62f7bb7a82fe23066fb0957d48ef677f6eeb8215f372f52e48bb32426"
 
+[[package]]
+name = "vercel"
+version = "0.1.0"
+dependencies = [
+ "anyhow",
+ "futures 0.3.31",
+ "http_client",
+ "schemars",
+ "serde",
+ "serde_json",
+ "strum 0.27.1",
+ "workspace-hack",
+]
+
 [[package]]
 name = "version-compare"
 version = "0.2.0"