benchmarks/apib: the port had been updated (+)
- Belatedly update to version 1.2.1 and sync port description
- Builds with CMake now and uses modern libraries instead of the Apache Portable Runtime (devel/apr1)
- While upstream asks for C++11, force C++17 because that's how Abseil C++ libraries are currently built, otherwise it won't link due to ABI incompatibilities
- Hook two provided tests to our framework (USES+=cmake:testing)