feat: add 'array_agg', 'max_by' function

[sunyeongchoi]

Issue #5747

array_agg

• Aggregates column values into an array

from tracks
aggregate {names = array_agg name}

max_by

• Returns the row with the maximum value for a specified column

from tracks
aggregate {longest_name = max_by name milliseconds}

[snth]

Hi @sunyeongchoi ,

Thank you for the PRs! I'm busy catching up on resolving some of the stale PRs and then will hopefully get to reviewing these soon.

[max-sixty]

the array functions require much more thought and language design. I think we can add functions for scalar functions, but we should not add array functions through this process

hope that's OK @sunyeongchoi ! I would welcome more scalar functions