liblog: benchmarks use google-benchmark library

Remove our circa 2014 snapshot of the google benchmarking library, and
use the now very stable google-benchmark suite. Some porting effort,
and deal with some benchmarking saddle points that take too long to
sort out. Focus on minimal API changes, _odd_ new behaviors, and style.

Test: liblog_benchmarks, ensure results in about the same range
Bug: 69423514
Change-Id: I2add1df9cb664333bcf983b57121ae151b26935b