Introduce LanguageModelToolUse::raw_input (#29322)

This is to enable alternative streaming solutions at the application
layer. I'm not sure we really should have performed parsing of the input
at this layer. Either way I want to experiment with streaming approaches
in a separate crate on a branch, and this will help.

/cc @maxdeviant @bennetbo @rtfeldman

Closes #ISSUE

Release Notes:

- N/A

crates/language_models/src/provider/google.rs

@@ -396,6 +396,7 @@ pub fn into_google(
                     Some(Part::FunctionCallPart(google_ai::FunctionCallPart {
                         function_call: google_ai::FunctionCall {
                             name: tool_use.name.to_string(),
+                            raw_args: tool_use.raw_input,
                             args: tool_use.input,
                         },
                     }))
@@ -537,6 +538,10 @@ pub fn map_to_language_model_completion_events(
                                                     id,
                                                     name,
                                                     is_input_complete: true,
+                                                    raw_input: function_call_part
+                                                        .function_call
+                                                        .raw_args
+                                                        .clone(),
                                                     input: function_call_part.function_call.args,
                                                 },
                                             )));