add beforeDeactivate and beforeActivate hook

[tbontb-iaq]

Currently, we have onMounted and onBeforeMount for mount, and the same applies to update and unmount. However, for activate and deactivated, we only have onActivated and onDeactivated, lacking onBeforeActivate and onBeforeDeactivate.

In vuejs/core#2349 (comment), I used onDeactivated to preserve the element's scroll position. However, by the time the onDeactivated hook is triggered, the element has already been detached from the DOM, and its scrollTop and scrollLeft are both 0.

[Daverine]

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[Daverine]

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