[Task]: Support list config for normal_dir and normal_test_dir of folder format

[fanchuanster]

What is the motivation for this task?

I am frustrated to merge multiple categories into a single normal dir (normal_test_dir as well), wondering it it makes sense to support list config for them?

dataset:
name: model
format: folder
path: /app/data/trainData
normal_dir: [folder1, folder2]
normal_test_dir: [testfolder1, testfolder2]

this is the error it throws when it's a list config:

TypeError: expected str, bytes or os.PathLike object, not ListConfig

Describe the solution you'd like

support list config for normal_dir and normal_test_dir of folder format

Additional context

No response

[harimkang]

I think it's a good feature for user convenience. I'll take a look and share my progress.