transcoder: Log benchmark transcoding params

Passed benchmarking configuration params - such as
source/target mime, bitrate, includeAudio and
transcodeVideo - through benchmark label and
logged in the custom csv reporter.

Bug: 177383910
Test: MediaTranscoderBenchmark --benchmark_out=Log.csv

Change-Id: I4460334538d2b91a142e7618f6c428afbe3b6815