Update tab_upload.py

This change resolves /issues/54

The code in `tab_upload.py` reads uploaded files 1024 bytes at a time. This is not efficient for large files on modern systems. 

`UploadFile.read()` maps to `RawIOBase.read()` which handles multiple reads to a stream internally. 

This change delegates stream io to the lower levels of the runtime.

self_hosting_machinery/webgui/tab_upload.py

@@ -149,11 +149,8 @@ async def _tab_files_upload(self, file: UploadFile):
             return JSONResponse(content=response_data, status_code=409)
         try:
             with open(tmp_path, "wb") as f:
-                while True:
-                    contents = await file.read(1024)
-                    if not contents:
-                        break
-                    f.write(contents)
+                contents = await file.read()
+                f.write(contents)
             os.rename(tmp_path, file_path)
         except OSError as e:
             log("Error while uploading file: %s" % (e or str(type(e))))