Support if function

[allenma]

Is your feature request related to a problem or challenge?

Most of the sql engines support if function, like spark, snowflake, mysql, etc. It is similar as Case expression, but only support one condition, the syntax is like:
IF( <condition> , <expr1> , <expr2> )
If condition evaluates to TRUE, returns expr1, otherwise returns expr2

Describe the solution you'd like

Add new build in function 'If'

Describe alternatives you've considered

No response

Additional context

No response

[Jefffrey]

I'll close this as being done by #16946 as it adds this function to the datafusion-spark crate