RFR: 8316135: Create release notes for JavaFX 21 [v4]

[Kevin Rushforth]

On Wed, 13 Sep 2023 12:21:49 GMT, Abhinay Agarwal <duke at openjdk.org> wrote:

>>> We should always use the base bug ID and never the backport ID, which for this bug is [JDK-8313227](https://bugs.openjdk.org/browse/JDK-8313227).
>> 
>> And to be clear I meant that the "base bug ID" for this bug is [JDK-8313227](https://bugs.openjdk.org/browse/JDK-8313227).
>
> my bad, the release notes has the correct base bug id 👍 
> 
> my local jfx21 release notes skipped [JDK-8313227](https://bugs.openjdk.org/browse/JDK-8313227) as it was labelled as `hgupdate-sync`.

This will need some careful JBS query logic when I update it to properly handle backports. The `hgupdate-sync` label is specific to the particular record (backport or main bug) for a particular code line. So the `hgupdate-sync` label on the main bug mean that the bug should be skipped, but only for jfx22 (by virtue of the fact that it is in jfx21).

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PR Review Comment: https://git.openjdk.org/jfx/pull/1239#discussion_r1327970439