Revert "[FIX] codegen/entity: Support multi argument extra attribute"

[Huliiiiii]

Reverts #2560

I have to revert this because the test input is incorrect. The test input should be split by ,.

Example:

[
    r#"serde(rename_all = "camelCase""#,
    r#" rename = "test")"#,
    r#"ts(export"#,
    r#" export_to = "path")"#
]

And in this case syn will panic because it can’t parse it into a valid TokenStream.