Primbench CSV output format

Primbench can write a CSV file alongside JSON results. CSV output is enabled when --csv-out is set to a file path. The CSV is a condensed view with one row per specialization.

Column	Description
index	Zero-based specialization index.
name	Specialization display name, quoted in the file.
bytes_per_second	Measured byte throughput.
gib_per_second	Throughput converted to GiB per second.
items_per_second	Measured item throughput.
noise_timeout	0 or 1.
noise_percent	Final noise percentage.

JSON output can be suppressed by setting --json-out to /dev/null while CSV output remains enabled.