Refactor benchmark options

[scotts]

Benchmark refactoring. A bunch of minor option-name changes to make them shorter. Bigger change is removing batch_parameters as an option from the core runner. The problem is that we apply it to all other benchmark scenarios - except the data loading benchmark scenario, since that is in fact a kind of batch scenario. This is confusing and not easy to extend.

We should figure out a way to generalize how to specify and run more scenarios, but I think a principle we should apply is that scenarios are self-contained. We don't want to have a scenario that implicitly applies itself to other scenarios.

For reference, the call:

python benchmarks/decoders/benchmark_decoders.py --decoders decord,decord_batch,torchcodec_public,torchcodec_core,torchaudio --min_run_seconds 20

Yields the results:

[- video=/home/scottas/github/torchcodec/benchmarks/decoders/../../test/resources/nasa_13013.mp4 h264 480x270, 13.013s 29.97002997002997fps -]
                           |  decode 10 uniform frames  |  decode 10 random frames  |  first 1 frames  |  first 10 frames  |  first 100 frames
1 threads: -----------------------------------------------------------------------------------------------------------------------------------
      DecordAccurateBatch  |            53.8            |           119.9           |       13.3       |        16.3       |        48.5      
      TorchAudio           |           183.5            |           197.4           |       11.2       |        13.1       |        33.4      
      DecordAccurate       |            52.8            |           119.0           |       13.0       |        16.3       |        66.7      
      TorchCodecCore       |            49.4            |            44.1           |       10.5       |        11.8       |        37.7      
      TorchCodecPublic     |            50.3            |            44.2           |       13.0       |        14.3       |        39.9      

Times are in milliseconds (ms).

[NicolasHug]

Nit: ideally for CLI (from the shell), all of those should be using - instead of _.
Specifying e.g. "--min-run-seconds" would still expose it as min_run_seconds in Python.