Mojo change: renaming `alias` to `comptime`

[denis (Denis Gurchenkov)]

@sora

I think alias provides the perfect amount of terminological strangeness to capture the semantical depth

Sora, thank you for capturing this so well and so elegantly. Many people share this sentiment to some degree. Alias is indeed strange enough so that it can be accepted as a separate term, but not too alien. This is a quality that comptime may or may not have, time will tell.