Add ability to override entire tv object from ui prop

[leeovery]

Description

Hi,

Being able to override the non-slot properties of the tv theme using the ui prop would be very handy.

Sometimes you don't want to override globally but just want a slightly different variation of a component. When trying to restyle variations it becomes quite tricky when you cant override anything other than the slots.

eg. if you wanted to override compoundVariants the only choice is to do it globally, which naturally effects all uses of that component.

A use case here is the UNavigationMenu. Accurately restyling hover effects etc is tricky without being able to override the whole tv object.

I was also thinking it would be nice to be able to define your own theme directory where you could define component tv objects which either replace or merge with the Nuxt ui versions.

Thanks
Lee

Additional context

No response