[pointer-animations-1] Prefix pointer() definition types

[tidoust]

Type definitions share a common namespace and the <axis> type is already defined in Scroll-driven Animations:
https://drafts.csswg.org/scroll-animations-1/#typedef-axis

This update prefixes the <axis> type (and <source> for consistency) with pointer- to disambiguate. Feel free to adjust the name as you see fit!

Note: As in Scroll-driven Animations, the spec defines the types with a noexport attribute. That seems fine to avoid accidental references from other modules. If that is also meant to create a module-specific namespace for type definitions, we may have a problem as editing tools and validators that I'm aware of and that leverage CSS syntax definitions do not expect that to be possible ;)

[ydaniv]

Thanks @tidoust! If I recall correctly I meant to reuse axis from Scroll-driven Animations, but I'm ok with merging this as is for now, it's still an early ED.
The source is probably better off prefixed.

[tidoust]

If I recall correctly I meant to reuse axis from Scroll-driven Animations

Up to you :) The noexport attribute of the <axis> definition would just need to be dropped in Scroll-driven Animations.