Deprecating $reactTo

[cesarParra]

Deprecating the $reactTo function for several reasons:

• It doesn't seem to work in a lot of situations, more than what I originally expected. I thought it was just for complex JS objects, but there are more unknowns situations where LWC simply doesn't update the values
• Having this not working sometimes but othertimes working can be very frustrating, and it doesn't make it clear when it can be used vs. computed, so by just keeping computed the interfaces are a bit more verbose to use, but it gives us consistency