enh: add prefix to generate_temporary_column_names

[MarcoGorelli]

This should generate a unique token which is not present in any of [f'{prefix}{col}' for col in df.columns]

[FBruzzesi]

I think the plotly use case is slightly different. I currently wrote the following helper function:

def _generate_temporary_column_name(n_bytes: int, columns: list[str]) -> str:
    """Wraps of Narwhals generate_temporary_column_name to generate a token
    which is guaranteed to not be in columns, nor in [col + token for col in columns]
    """
    counter = 0
    while True:
        # This is guaranteed to not be in columns by Narwhals
        token = nw.generate_temporary_column_name(n_bytes, columns=columns)
        if token not in {f"{c}{token}" for c in columns}:
            return token

        counter += 1
        if counter > 100:
            msg = (
                "Internal Error: Narwhals was not able to generate a column name with "
                f"{n_bytes=} and not in {columns}"
            )
            raise AssertionError(msg)