Support JSON lines with missing columns

[albertvillanova]

Support JSON lines with missing columns.

Fix #7169.

The implemented test raised:

datasets.table.CastError: Couldn't cast
age: int64
to
{'age': Value(dtype='int32', id=None), 'name': Value(dtype='string', id=None)}
because column names don't match

Related to:

• Support JSON lines with missing struct fields #7160
• Support JSON lines with empty struct #7162

[HuggingFaceDocBuilderDev]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.