Concurrency: Use JSPromise.Result instead of Swift.Result for JSPromise.result

To reduce burden type casting, it's better to remove the wrapper from
the API.

Author: kateinoigakukun

Sources/JavaScriptEventLoop/JavaScriptEventLoop.swift

@@ -227,7 +227,7 @@ public extension JSPromise {
     }
 
     /// Wait for the promise to complete, returning its result or exception as a Result.
-    var result: Swift.Result<JSValue, JSException> {
+    var result: JSPromise.Result {
         get async {
             await withUnsafeContinuation { [self] continuation in
                 self.then(
@@ -236,7 +236,7 @@ public extension JSPromise {
                         return JSValue.undefined
                     },
                     failure: {
-                        continuation.resume(returning: .failure(JSException($0)))
+                        continuation.resume(returning: .failure($0))
                         return JSValue.undefined
                     }
                 )