Add some thunderfx report functions to docs

[crcrpar]

I think the two below worth adding to somewhere, maybe https://github.com/Lightning-AI/lightning-thunder/blob/main/docs/source/reference/dynamo/index.rst

• lightning-thunder/thunder/dynamo/report.py

  Line 1282 in 5bdf5bc

  def thunderfx_benchmark_report(

• lightning-thunder/thunder/dynamo/report.py

  Line 1205 in 5bdf5bc

  def thunderfx_benchmark_report_from_splits(

cc @Borda @lantiga