Export gki/testdata/testkey_rsa4096.pem to Bazel rules. am: 2208a03d87 am: 40ccb64f11 am: 0101cfe925 am: 206e5c33d3 am: 303e8dfaa9

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

Change-Id: I57c3e14600888fe3e04c1a797c6d965c33e93feb
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>