[function] last_day

[wangsimo0]

Feature request

as mentioned in #15385, last_day need to be supported. However last day can be used in month/quarter/year. So I think it's better to support this feature flexibly.

here is my proposal:

description

Returns the last day of the specified date part for a date or datetime.

syntax

LAST_DAY ( <date_or_datetime_expr> , [<date_part>])

in which,
date_or_datetime_expr is a date or datetime expression
date_part is an optional parameter. can be month, quarter,year, default to month.
the return value is always a date.

[vendanner]

here