[Feature] Add csv param to datasets

[okotaku]

Motivation

We can assign the CSV name to the dataset parameter as csv.

Use cases (Optional)

train_dataloader = dict(
    dataset=dict(
        csv='metadata2.csv'),
)

Checklist

Before PR:

• Pre-commit or other linting tools are used to fix the potential lint issues.
• Bug fixes are fully covered by unit tests, the case that causes the bug should be added in the unit tests.
• The modification is covered by complete unit tests. If not, please add more unit test to ensure the correctness.
• The documentation has been modified accordingly, like docstring or example tutorials.