Add needed status check on the merge_group

When adding an approved PR to the merge queue, the required status
checks of the workflows are missing, which prevents the PR getting
merged. This commit is intended to trigger merge group checks with
Github Actions, so that the workflows will report the needed status
checks.

Signed-off-by: Wen Liang <liangwen12year@gmail.com>

.github/workflows/python-unit-test.yml

@@ -3,6 +3,11 @@
 name: Python Unit Tests
 on:  # yamllint disable-line rule:truthy
   pull_request:
+  merge_group:
+    branches:
+      - main
+    types:
+      - checks_requested
   push:
     branches:
       - main