attributes: consider supporting more `_ATTRIBUTE` macros

[achabense]

Currently we have _NODISCARD and _FALLTHROUGH, which will expand to [[attribute]] if supported, or nothing otherwise.

I think it will be very helpful to support more _ATTRIBUTE macros for standard attributes. For example, in this pr, we can make the code much cleaner if we have _LIKELY and _UNLIKELY.

[achabense]

I think this is useless as a separate issue; we can introduce these macros whenever there is real need for them.