Deprecate `Ember.{isEmpty,isBlank,isNone,isPresent}`

[locks]

emberjs/ember.js#5543 (comment)

Almost certainly Ember.{isEmpty,isBlank,isNone,isPresent} should be deprecated. They don’t really add value over the normal JS that you would write in each case, and they generally have negative cognitive impact on the code in question...

[snewcomer]

On it! Should finish it up by tomorrow.

[bekzod]

this can be closed no ? since there is rfcs open already

[bertdeblock]

👋 Can we close this issue in favour of the open RFC: #334?

[locks]

Tracked at the respective RFC!