Run the encode/decode tests as benchmarks. These are trivial microbenchmarks
and not representative of real-world usage, but serve as a useful overview
of the relative cost of various operations and are handy for profiling
specific narrow scenarios.
When run with the -v1 flag, benchmark the v1 implementation for comparison.
Change-Id: I469dd6759bef50e2bd039327095f82d29d70b8fc
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/171120
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>
