[FEATURE] Remove benchmarker CSV input in favor of JSON

[Kern--]

Description

#908 added support for specifying bechmarks in a JSON file instead of CSV. #938 Adds additional, image-specific options such as GPU support and mounts, but these are only available via the JSON configuration.

Describe the solution you'd like

Since the JSON option is easier to read and more featureful, we should remove CSV as an option and always expect the benchmark file to be JSON.

Describe any alternative solutions/features you've considered

We could add support for optional parameters to CSV (e.g. by having specific key/value pairs at the end of the options, having a field that has key=value pairs that we parse, etc).

This seems like a bad way to go because it would take more effort and parsing to reimplement features we get for free with JSON.

Any additional context or information about the feature request

No response