Merge values and handlers in fork

[zerobias]

Proposal

Merge values and handlers in fork to single property. Effector can choose between store and effect automatically, so possibly we can merge them to single property.

fork({
  fill: [
    [$foo, 'foo'],
    [$bar, 1],
    [requestFx, () => null],
    [getUsersFx, () => []]
  ]
})

Pros: easier to use, like useStore and useEvent was merged to useUnit
Cons: another breaking change, benefits of merge not obvious, as many people still write useUnit(stores) and useUnit(eventsOrEffect) in two calls to preserve semantic distinction

Not sure which property name could be used and whether we need to go in this direction so I create this issue to remember that we have this option