RFR: 8272870: Add convenience factory methods for border and background [v3]

Sun Sep 19 01:36:40 UTC 2021

On Wed, 15 Sep 2021 11:16:39 GMT, Ambarish Rapte <arapte at openjdk.org> wrote:

> Above one will just be uniform with existing doc.

In this case it doesn't matter much, but in general I don't like many places of the `Background` and `Border` docs as they stand :)
I already looked at them as a starting point when creating the initial commit.

-------------

PR: https://git.openjdk.java.net/jfx/pull/610