[CI] Avoid lint and ut for PR push (#5762)

1. Don't run lint and ut again once the PR is merged to save CI resource
2. Update codecov every 4 hour
3. rename `model_downloader` to suitable name
4. update schedule job to better time.

- vLLM version: v0.13.0
- vLLM main:
2f4e6548ef

Signed-off-by: wangxiyuan <wangxiyuan1007@gmail.com>

.github/workflows/schedule_test_vllm_main.yaml

@@ -17,9 +17,9 @@
 name: vLLM Main Schedule Test
 
 on:
-  # Run full e2e tests per 4h
+  # Run full e2e tests UTC+8: 10am, 16pm, 22pm, 4am
   schedule:
-    - cron: '0 */4 * * *'
+    - cron: '0 2,8,14,20 * * *'
   workflow_dispatch:
 
 # Bash shells do not use ~/.profile or ~/.bashrc so these shells need to be explicitly