Add support for OpenAI GPT-4.1 models (#28708)

Release Notes:

- Add support for OpenAI GPT-4.1 via Copilot Chat and OpenAI API

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Co-authored-by: Danilo Leal <daniloleal09@gmail.com>
Co-authored-by: Bennet Bo Fenner <bennetbo@gmx.de>

crates/language_models/src/provider/copilot_chat.rs

@@ -215,6 +215,7 @@ impl LanguageModel for CopilotChatLanguageModel {
                 let model = match self.model {
                     CopilotChatModel::Gpt4o => open_ai::Model::FourOmni,
                     CopilotChatModel::Gpt4 => open_ai::Model::Four,
+                    CopilotChatModel::Gpt4_1 => open_ai::Model::FourPointOne,
                     CopilotChatModel::Gpt3_5Turbo => open_ai::Model::ThreePointFiveTurbo,
                     CopilotChatModel::O1 | CopilotChatModel::O3Mini => open_ai::Model::Four,
                     CopilotChatModel::Claude3_5Sonnet