Import libtest-mimic crate. am: e2bd850ae7 am: f6c6671e0c am: 9681cdf00a am: 725310cd0a

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/libtest-mimic/+/2498258

Change-Id: I403ae0d44d7ea3e2746be27d9b17f6155fe07c2d
Signed-off-by: Automerger Merge Worker <[email protected]>