[experiment infra] Change the directory structure of experiment results

[TheRootOf3]

Please change the structure of the experiment directory to the following:

experiment_data
└── eval_results
     ├── seq-lr-1e-6-4-128-20-llama-3-8B-harmful-squad
     │   ├── hamrfulness 
     │   ├── truthfulqa
     │   └── lm_eval_harness
     ├── ...
     └── seq-lr-1e-6-64-1024-60-llama-3-8B-harmful-squad

[Willmish]

Added in #106 (the scheduling scripts for sequential runs 1e-6, 5e-6, 1e-5 stick to this structure