fix(useActiveElement/useFocusWithin): replace computedWithControl with locally tracked ref

[jaketig]

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⚠️ Slowing down new functions

Warning: Slowing down new functions

As the VueUse audience continues to grow, we have been inundated with an overwhelming number of feature requests and pull requests. As a result, maintaining the project has become increasingly challenging and has stretched our capacity to its limits. As such, in the near future, we may need to slow down our acceptance of new features and prioritize the stability and quality of existing functions. Please note that new features for VueUse may not be accepted at this time. If you have any new ideas, we suggest that you first incorporate them into your own codebase, iterate on them to suit your needs, and assess their generalizability. If you strongly believe that your ideas are beneficial to the community, you may submit a pull request along with your use cases, and we would be happy to review and discuss them. Thank you for your understanding.

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Description

useActiveElement and useFocusWithin are currently broken due to computedWithControl being used inside of computed triggering the following warning:

[Vue warn] Computed is still dirty after getter evaluation, likely because a computed is mutating its own dependency in its getter. State mutations in computed getters should be avoided.  Check the docs for more details: https://vuejs.org/guide/essentials/computed.html#getters-should-be-side-effect-free

This PR replaces computedWithControl with a locally tracked ref so useActiveElement can be used inside a computed as done in useFocusWithin:

vueuse/packages/core/useFocusWithin/index.ts

Lines 23 to 25 in 1b67d96

	const activeElement = useActiveElement(options)
	const targetElement = computed(() => unrefElement(target))
	const focused = computed(() => (targetElement.value && activeElement.value) ? targetElement.value.contains(activeElement.value) : false)

Additional context

related issues: #3799, #3794, #3787, #3774, #3760

upstream issue: vuejs/core#10341