RFC: Unify all "APIs" and namings

[Kelin2025]

Case

Currently keyval methods such createListApi, createItemApi, createSelection etc. return different shapes, but they have some common parts

Solution

1. Unify shapes that are returned from methods
2. Unify methods naming (createSelection -> createSelectionApi)

const $kv = createListApi({ ... })
const $selection = createSelectionApi({ ... })
const $mapped = createMapApi({ ... })

$kv.state.store
$kv.state.items
$selection.state.store
$selection.state.items