Latest Haxe should imply latest neko

[Simn]

We currently have an issue where the latest Haxe version depends on the latest neko version, but setup-haxe installs neko 2.4.0 by default. Since there's already a resolveFromHaxeVersion function, I think it should match latest/nightly accordingly.

The URLs are:

https://build.haxe.org/builds/neko/linux64/neko_latest.tar.gz
https://build.haxe.org/builds/neko/mac-universal/neko_latest.tar.gz
https://build.haxe.org/builds/neko/windows64/neko_latest.zip