[REGRESSION] Multiple uploads not working on iOS (#2738)

* Update React Native to 0.63.4

* Fix multiple uploads not working on iOS

app/utils/fileUpload/index.ios.js

@@ -1,46 +1,50 @@
+class Upload {
+	constructor() {
+		this.xhr = new XMLHttpRequest();
+		this.formData = new FormData();
+	}
+
+	then = (callback) => {
+		this.xhr.onload = () => callback({ respInfo: this.xhr });
+		this.xhr.send(this.formData);
+	}
+
+	catch = (callback) => {
+		this.xhr.onerror = callback;
+	}
+
+	uploadProgress = (callback) => {
+		this.xhr.upload.onprogress = ({ total, loaded }) => callback(loaded, total);
+	}
+
+	cancel = () => {
+		this.xhr.abort();
+		return Promise.resolve();
+	}
+}
+
 class FileUpload {
-	_xhr = new XMLHttpRequest();
-
-	_formData = new FormData();
-
 	fetch = (method, url, headers, data) => {
-		this._xhr.open(method, url);
+		const upload = new Upload();
+		upload.xhr.open(method, url);
 
 		Object.keys(headers).forEach((key) => {
-			this._xhr.setRequestHeader(key, headers[key]);
+			upload.xhr.setRequestHeader(key, headers[key]);
 		});
 
 		data.forEach((item) => {
 			if (item.uri) {
-				this._formData.append(item.name, {
+				upload.formData.append(item.name, {
 					uri: item.uri,
 					type: item.type,
 					name: item.filename
 				});
 			} else {
-				this._formData.append(item.name, item.data);
+				upload.formData.append(item.name, item.data);
 			}
 		});
 
-		return this;
+		return upload;
-	}
-
-	then = (callback) => {
-		this._xhr.onload = () => callback({ respInfo: this._xhr });
-		this._xhr.send(this._formData);
-	}
-
-	catch = (callback) => {
-		this._xhr.onerror = callback;
-	}
-
-	uploadProgress = (callback) => {
-		this._xhr.upload.onprogress = ({ total, loaded }) => callback(loaded, total);
-	}
-
-	cancel = () => {
-		this._xhr.abort();
-		return Promise.resolve();
 	}
 }