Export gki/testdata/testkey_rsa4096.pem to Bazel rules. am: 2208a03d87 am: 40ccb64f11

Original change: https://android-review.googlesource.com/c/platform/system/tools/mkbootimg/+/2128235

Change-Id: I7b9f5d76bb8932fd2cc54a540f74502c86292f8f
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>