feat: improve decimal API

I found a problem when I tested the code. Is there something wrong?

```sql
CREATE TABLE default.dev
(
test Decimal32(2)
)
ENGINE = MergeTree()
ORDER BY tuple();
```
```go
var data proto.ColDecimal32
data.Append(1)
if err := c.Do(ctx, ch.Query{
Body: "INSERT INTO default.dev VALUES",
Input: []proto.InputColumn{
{
Name: "test",
Data: data,
},
},
}); err != nil {
panic(err)
}
```
run error:
```
panic: handle packet: NUMBER_OF_ARGUMENTS_DOESNT_MATCH (42): DB::Exception: Decimal data type family must have exactly two arguments: precision and scale
````

ColDecimal32/ColDecimal64/ColDecimal128 the same