Add build files for strum crate

- cargo_embargo.json generated using `cargo_embargo autoconfig
  cargo_embargo.json` without modifications
- Android.bp generated using `cargo_embargo generate cargo_embargo.json`
  and added `license` rules manually.

Bug: 305781607
Test: m libstrum
Change-Id: Idd80d0fa2e6e4aa644b84bd931ef5143999f0b7d
2 files changed