feat(VCarousel): add stopOnHover prop to pause cycling on hover

[mixelburg]

Fixes #10544

Adds a stop-on-hover prop to VCarousel. When set alongside cycle, the auto-cycling pauses while the user hovers over the carousel and resumes when they move away.

The implementation adds an isHovered ref and onMouseenter/onMouseleave handlers on the root VWindow. The handlers are no-ops unless stopOnHover is true, so there's no runtime cost for the default case. The startTimeout guard also checks isHovered.value so a programmatic restart (e.g. slide change) won't queue the next tick while hovering.

Usage:

<v-carousel cycle :interval="3000" stop-on-hover>
  <v-carousel-item v-for="item in items" :key="item.src" :src="item.src" />
</v-carousel>

[J-Sek]

new prop qualifies this for dev branch