feat: to_decimal support more types

[youngsofun]

now only support string

for other types return error like:

 select to_decimal(1.2::float, 3, 2);
error: APIError: QueryFailed: [1065]error: 
  --> SQL:1:8
  |
1 | select to_decimal(1.2::float, 3, 2)
  |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ no function matches signature `to_decimal(3, 2)(Float32, UInt8, UInt8)`, you might need to add explicit type casts.

have to write as select to_decimal(3, 2)(1.2::float) or 1.2::float::decimal(3,2)

[wubx]

https://docs.snowflake.com/en/sql-reference/functions/to_decimal