ci: replace ubuntu-latest runner with sm-standard-2 across workflows (#8112)

* ci: replace ubuntu-latest runner with sm-standard-2 across workflows

* ci: keep scheduled-validation monitors on hosted runners

The freshness and watchdog jobs report stalled scheduled validations.
Running them on the same sm-standard-2 pool means a pool outage stalls
the monitors too, so nothing reports it.

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Co-authored-by: overtrue <anzhengchao@gmail.com>

.github/workflows/package.yml

@@ -77,7 +77,7 @@ jobs:
       (github.event.workflow_run.conclusion == 'success' &&
        github.event.workflow_run.event == 'push' &&
        github.event.workflow_run.head_branch != 'main')
-    runs-on: ubuntu-latest
+    runs-on: sm-standard-2
     timeout-minutes: 10
     outputs:
       version: ${{ steps.resolve.outputs.version }}
@@ -229,7 +229,7 @@ jobs:
   package:
     name: Package (${{ matrix.arch }}-${{ matrix.libc }})
     needs: resolve
-    runs-on: ubuntu-latest
+    runs-on: sm-standard-2
     timeout-minutes: 30
     strategy:
       fail-fast: false
@@ -619,7 +619,7 @@ jobs:
     name: Summary
     needs: [ resolve, package ]
     if: always()
-    runs-on: ubuntu-latest
+    runs-on: sm-standard-2
     timeout-minutes: 5
     steps:
       - name: Print summary