Upgrade rust/crates/protobuf to 2.18.0

Bug: 170256643
Test: atest -c --include-subdirs external/rust/crates
Test: atest -c --host --include-subdirs external/crosvm
Change-Id: Idbf928c5a7e95e75acf492b67c3bbe3f3a83ad51
5 files changed
tree: e959c72d21300af101bd34042b53f95442f38fc8
  1. benches/
  2. out/
  3. src/
  4. .cargo_vcs_info.json
  5. Android.bp
  6. build.rs
  7. Cargo.toml
  8. Cargo.toml.orig
  9. LICENSE.txt
  10. METADATA
  11. MODULE_LICENSE_BSD_LIKE
  12. OWNERS
  13. post_update.sh
  14. README.md
  15. regenerate.sh
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.