Boolean properties as HTML binary attributes #14761

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[ ] bug report => search github for a similar issue or PR before submitting
[x] feature request
[ ] support request => Please do not submit support request here, instead see https://github.com/angular/angular/blob/master/CONTRIBUTING.md#question

Current behavior
Currently when you have a boolean property and bind it to true|false you have to use property binding, i.e

<my-button [rounded]="true"></my-button>

Expected behavior

The following code snippet should set the rounded property to true:

<my-button rounded></my-button>

while the snippet bellow should bind it to false:

<my-button ></my-button>

What is the motivation / use case for changing the behavior?
This mimics the behavior of HTML binary attributes as well as how React threads such properties.

Of course property binding to should still works.