Migrate to cargo_embargo. am: 17c785e114 am: 3f51dd0bc9 am: b7f32949f0

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/proc-macro2/+/2830192

Change-Id: I9715ea86a33241941c80cc39c911402151730331
Signed-off-by: Automerger Merge Worker <[email protected]>