Upgrade rust/crates/protobuf to 2.20.0 am: 914311bd1f

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/protobuf/+/1543445

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I82f87af4172d2d2fe8683e3e63a65618f68320ae
tree: 15427d5f69c1b9fe3ec75ee2be999f2750ca1164
  1. benches/
  2. out/
  3. patches/
  4. src/
  5. .cargo_vcs_info.json
  6. Android.bp
  7. build.rs
  8. Cargo.toml
  9. Cargo.toml.orig
  10. LICENSE.txt
  11. METADATA
  12. MODULE_LICENSE_MIT
  13. OWNERS
  14. README.md
  15. regenerate.sh
  16. TEST_MAPPING
README.md

How to develop rust-protobuf itself

cargo test --all to build everything.

If code generator is changed, code needs to be regenerated, see regenerate.sh.