[browser] Fix computing destination sub path and publish extension target path in Wasm SDK (#105458)

Author: maraf

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/AssetsComputingHelper.cs

@@ -107,7 +107,9 @@ public static string GetCandidateRelativePath(ITaskItem candidate, bool fingerpr
         {
             fileName = Path.GetFileNameWithoutExtension(destinationSubPath);
             extension = Path.GetExtension(destinationSubPath);
-            subPath = destinationSubPath.Substring(fileName.Length + extension.Length);
+            subPath = Path.GetDirectoryName(destinationSubPath);
+            if (!string.IsNullOrEmpty(subPath))
+                subPath += "/";
         }
 
         string relativePath;

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/GenerateWasmBootJson.cs

@@ -336,7 +336,7 @@ public void WriteBootJson(Stream output, string entryAssemblyName)
                         resourceList = new();
                         resourceData.extensions[extensionName] = resourceList;
                     }
-                    var targetPath = resource.GetMetadata("TargetPath");
+                    var targetPath = endpointByAsset[resource.ItemSpec].ItemSpec;
                     Debug.Assert(!string.IsNullOrEmpty(targetPath), "Target path for '{0}' must exist.", resource.ItemSpec);
                     AddResourceToList(resource, resourceList, targetPath);
                     continue;
@@ -431,7 +431,7 @@ void AddResourceToList(ITaskItem resource, ResourceHashesByNameDictionary resour
         {
             if (!resourceList.ContainsKey(resourceKey))
             {
-                Log.LogMessage(MessageImportance.Low, "Added resource '{0}' to the manifest.", resource.ItemSpec);
+                Log.LogMessage(MessageImportance.Low, "Added resource '{0}' with key '{1}' to the manifest.", resource.ItemSpec, resourceKey);
                 resourceList.Add(resourceKey, $"sha256-{resource.GetMetadata("Integrity")}");
             }
         }