Upgrade gdbstub_arch to 0.3.0 am: 49667facd5 am: fbc3c78edc am: ff57130de2

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/gdbstub_arch/+/2878119

Change-Id: I32451111f3768defb751cf0dd2f6d2c75298ffbb
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>