Add BCR presubmit testing for Bazel 8.x and rolling

From https://github.com/bazelbuild/bazel-central-registry/pull/6477

(Thanks @jwnimmer-tri)

Change-Id: Ib2a38095602405574172f5e32539fda34ef15208
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/83927
Auto-Submit: Lily Chen <chlily@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
Commit-Queue: Lily Chen <chlily@google.com>
Reviewed-by: David Benjamin <davidben@google.com>

.bcr/presubmit.yml

diff --git a/.bcr/presubmit.yml b/.bcr/presubmit.yml
index 44e4b7a..30f5c86 100644
--- a/.bcr/presubmit.yml
+++ b/.bcr/presubmit.yml
@@ -6,7 +6,7 @@
   linux_platforms:
     - debian11
     - ubuntu2204
-  bazel: [7.x]
+  bazel: [7.x, 8.x, rolling]
 tasks:
   verify_targets_on_linux:
     name: Verify build targets on Linux