Public API: effect without stop

[jods4]

What problem does this feature solve?

The public API is unusable without creating memory leaks.
effect is exposed:
https://github.com/vuejs/vue-next/blob/master/packages/runtime-core/src/apiReactivity.ts#L12
but stop is not.

What does the proposed API look like?

Either remove effect or expose stop.

Note
The publicly exposed computed and watch are linked the component lifetime when used inside setup (computed is not the one exposed by reactivity but a wrapper).
Without effect, there is no way to do a computed or watch inside setup that is not linked to the component.
I have no use case for that, just noting.