Fix a bunch of issues revealed by the upgraded clippy
- update UUID library for improved uuid! parser macro
- make #[cfg(test)] block the last thing in a file
- call .to_string() instead of format! without interpolation
- use infallible conversion instead of try_into().expect
- remove redundant "Error" suffix from enum variant names
- remove unused type
These are intertwined: older versions of Rust don't support the newer
NDK, but the newer Rust can't successfully compile BoringSSL against
the older NDK.
This requires a boring-sys update to find the Android NDK sysroot in
the right place.
