gha-ci: use Bazel 8.x and run daily on schedule

Protobuf 36.2 requires at least Bazel 8.0.0. Also add a daily cron
schedule in addition to running on push.

Change-Id: I8490eaa59a186e61f799917ae857cd1c01d27f5d
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/855721
Reviewed-by: Dennis Shao <shaod@google.com>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

.github/workflows/test.yml

diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index df0d634..26ffd2b 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -1,4 +1,7 @@
-on: [push]
+on:
+  push:
+  schedule:
+    - cron: '0 0 * * *'
 name: Test
 jobs:
   test:
@@ -28,6 +31,6 @@
         key: ${{ runner.os }}-${{ hashFiles('integration_test.go') }}
     - name: Test
       env:
-        # Protobuf 30 does not yet support anything newer than Bazel 7
-        USE_BAZEL_VERSION: 7.x
+        # Protobuf 36 requires at least Bazel 8
+        USE_BAZEL_VERSION: 8.x
       run: go test -run='^TestIntegration$' -v -timeout=60m -count=1 -failfast "$@"