rpc: Remove llm module in favor of zed_llm_client (#28900)

This PR removes the `llm` module of the `rpc` crate in favor of using
the types from the `zed_llm_client`.

Release Notes:

- N/A

crates/collab/src/llm/db.rs

@@ -8,9 +8,9 @@ mod tests;
 
 use collections::HashMap;
 pub use ids::*;
-use rpc::LanguageModelProvider;
 pub use seed::*;
 pub use tables::*;
+use zed_llm_client::LanguageModelProvider;
 
 #[cfg(test)]
 pub use tests::TestLlmDb;

crates/collab/src/llm/db/tests/provider_tests.rs

@@ -1,5 +1,5 @@
 use pretty_assertions::assert_eq;
-use rpc::LanguageModelProvider;
+use zed_llm_client::LanguageModelProvider;
 
 use crate::llm::db::LlmDatabase;
 use crate::test_llm_db;