Refa: convert download_img to async (#13477)

### What problem does this PR solve?

Convert download_img to async.

### Type of change

- [x] Refactoring
- [x] Performance Improvement

common/misc_utils.py

@@ -27,16 +27,16 @@ import uuid
 
 from concurrent.futures import ThreadPoolExecutor
 
-import requests
 
 def get_uuid():
     return uuid.uuid1().hex
 
 
-def download_img(url):
+async def download_img(url):
     if not url:
         return ""
-    response = requests.get(url)
+    from common.http_client import async_request
+    response = await async_request("GET", url)
     return "data:" + \
         response.headers.get('Content-Type', 'image/jpg') + ";" + \
         "base64," + base64.b64encode(response.content).decode("utf-8")