[ES|QL] Create EARLIEST/LATEST aliases for First/Last #141681
Description
This issue was created out of a small number of remaining work from #108385 that was deemed not necessary for a tech preview, essentially all the items from the "Things to circle back to after tech preview" section in the aforementioned ticket.
The issue
Make aliases that default to @timestamp for the second parameter, and call them EARLIEST/LATEST. For example EARLIEST(foo) will be like syntactic sugar for FIRST(foo, @timestamp)