Deprecate `Function.prototype.{on,observes,property}`

[locks]

Ember has been moving away from extending native prototypes due to the confusion that this causes users.
The most recent case of this was part of the Ember.String deprecation RFC, where the package was extracted and prototype extensions moved to a support addon.

To continue on this path, deprecation Function.prototype.{on,observes,property} should be investigated.
They have non-extension equivalents, both in the import Ember from 'ember'; and import { … } from '@ember/…'.

[sarupbanskota]

I'll take this up

[locks]

It is ddoonnneee. Thank you @sarupbanskota!