chore(ci): test Bazel 8 and 9 on BCR (#2364)

Author: alexeagle

.bcr/presubmit.yml

@@ -1,7 +1,7 @@
 bcr_test_module:
     module_path: 'e2e/bzlmod'
     matrix:
-        bazel: ['7.x', '6.x']
+        bazel: ['rolling', '8.x', '7.x', '6.x']
         platform: ['debian10', 'macos', 'ubuntu2004', 'windows']
     tasks:
         run_tests: