[test-suite] Update test-suite microbenchmarks to use JSON (fix bug 41327)

Google benchmark is hoping to drop the CSV output format. This updates the microbenchmark module to use the JSON output.

This fixes PR41327

Reviewers: lebedev.ri

https://reviews.llvm.org/D60205


git-svn-id: https://llvm.org/svn/llvm-project/test-suite/trunk@357704 91177308-0d34-0410-b5e6-96231b3b80d8