[Tracing] Add tracing to functions in Isolate::run (#24558)

There are some missing spans in `Isolate::run` so this aims to capture some of the missing execution time.

GitOrigin-RevId: baea64010a124a53fac037cfaa4e3069490f2189

Author: jordanhunt22

crates/isolate/src/isolate.rs

@@ -262,6 +262,7 @@ impl<RT: Runtime> Isolate<RT> {
         Ok(())
     }
 
+    #[minitrace::trace]
     pub async fn start_request<E: IsolateEnvironment<RT>>(
         &mut self,
         environment: E,

crates/isolate/src/request_scope.rs

@@ -148,6 +148,7 @@ impl<RT: Runtime, E: IsolateEnvironment<RT>> RequestState<RT, E> {
 }
 
 impl<'a, 'b: 'a, RT: Runtime, E: IsolateEnvironment<RT>> RequestScope<'a, 'b, RT, E> {
+    #[minitrace::trace]
     pub async fn new(
         scope: &'a mut v8::HandleScope<'b>,
         handle: IsolateHandle,