Add dateadd function

[osipovartem]

New function should support this signature

DATEADD( <date_or_time_part>, <value>, <date_or_time_expr> )

Detailed description here
https://docs.snowflake.com/en/sql-reference/functions/dateadd
Basic implementation can be taken from
https://github.com/apache/datafusion/tree/main/datafusion/functions/src/datetime

[DanCodedThis]

I looked into date_trunc, it cleared some things up. Still looking for the "addition op" as it was in this PR in datetime.rs line 202: https://github.com/apache/datafusion/pull/3110/files#diff-6acdb260dee24439d23b730937a21c579000adc11798f06b9d4517e2467c5dcb

Later removed here: apache/datafusion#3153

I have a question, will we have a problem supporting "weeks", since I don't see a type for this here: https://docs.rs/datafusion/latest/datafusion/common/arrow/datatypes/enum.IntervalUnit.html

"Year" is supported through some internal conversion to MonthDayNano, if I'm not mistaken.

[DanCodedThis]

With the last commit, I can say that if were to use the internal types, we need to extend the sql parser for this query "select dateadd('''0 days''', 3,'''2024-12-26''')" (now it works like this "3 days" => IntervalMonthDayNano(3)):

1. "days" => IntervalMonthDayNano(0), this one can be changed to use utf8 without sql parser extension (but it is probably right to extend specifically the parser)
2. "days, 3" => IntervalMonthDayNano(3) - may bring many horrible problems

Why do we want to use internal types? - Because the addition is built in, we can just add most of the variations and it will work out of the box

[DanCodedThis]

Needs testing, seems to work