Add experimental mercury edit prediction provider (#44256)

Release Notes:

- N/A

---------

Co-authored-by: Ben Kunkle <ben@zed.dev>
Co-authored-by: Max Brunsfeld <maxbrunsfeld@gmail.com>

crates/language_models/src/provider/open_ai.rs

@@ -438,7 +438,7 @@ pub fn into_open_ai(
         messages,
         stream,
         stop: request.stop,
-        temperature: request.temperature.unwrap_or(1.0),
+        temperature: request.temperature.or(Some(1.0)),
         max_completion_tokens: max_output_tokens,
         parallel_tool_calls: if supports_parallel_tool_calls && !request.tools.is_empty() {
             // Disable parallel tool calls, as the Agent currently expects a maximum of one per turn.