The 'getBigDecimal' method has a precision of 0 by default

[SurelySomeday]

When using a 'getBigDecimal' query, the 'ClickHouse DoubleValue' is returned, but when converting to 'BigDecimal', use 'scale=0' directly, which will result in a loss of precision.
Although there is such a way as 'getBigDecimal(v, scale)', the current JDBC specification should be deprecated, and the method 'getBigDecimal(v)' is normally used. I think it would be better to use 'BigDecimal.valueOf(v)' to maintain the correct precision.

[zhicwu]

Thanks @SurelySomeday, I'll fix this in patch9.