Move the benchmarks using the common protobuf datasets out of proto/ and
into their own directory. Add benchmarks for text and JSON.
Move initialization out of the Benchmark function to avoid including it
in CPU/memory profiles.
We could put benchmarks in each individual package (proto, prototext,
etc.), but the need for common infrastructure around managing the test
data makes it simpler to keep the benchmarks together. Also, it's nice
to have a one-stop overview of performance.
Change-Id: I17c37efb91b2413fc43ab1b4c35bff2e1330bc0a
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/183245
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>
