Revert^2 "add rust_toolchain_rustc_prebuilt module type" am: 9333ac12 am:...

Revert^2 "add rust_toolchain_rustc_prebuilt module type" am: 9333ac12 am: c640053d am: 8de7c130

Original change: https://android-review.googlesource.com/c/platform/build/soong/+/2746466



Change-Id: Iae3daf6ed9ea39c62fce8074a982c7ebfcf7e85c
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>