RFR: JDK-8304439: Subscription based listeners [v10]

[Kevin Rushforth]

On Tue, 11 Jul 2023 23:05:21 GMT, John Hendrikx <jhendrikx at openjdk.org> wrote:

>> Makes `Subscription` public (removing some of its methods that are unnecessary), and adds methods that can provide `Subscription`s in `ObservableValue`.
>
> John Hendrikx has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Add since tag to Subscription

modules/javafx.base/src/main/java/javafx/beans/Subscription.java line 35:

> 33:  * to keep track of how it was created.
> 34:  *
> 35:  * @Since 21

Needs to be lower-case `s`

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

PR Review Comment: https://git.openjdk.org/jfx/pull/1069#discussion_r1260369855