RFR: 8343196: Add build property to identify experimental builds of JavaFX [v6]

[Ambarish Rapte]

> Introduce a new build property `jfx.experimental.release.suffix` to be used for the early access builds of an under development feature in JavaFX.
> This property would be set to a value ONLY in a branch specific to an experiment in [jfx-sandbox](https://github.com/openjdk/jfx-sandbox) repo.
> For example:
> For the metal branch in jfx-sandbox repo, it would be set to `-metal`.  The javafx.version for the early access build generated from that branch would be `24-metal`.
> 
> And it would always be empty for master branch in both main jfx repo and in jfx-sandbox repo.
> This change has no effect on a regular developer build from master branch.

Ambarish Rapte has updated the pull request incrementally with one additional commit since the last revision:

  Update build.gradle
  
  Review correction
  
  Co-authored-by: Kevin Rushforth <kevin.rushforth at oracle.com>

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

Changes:
  - all: https://git.openjdk.org/jfx/pull/1637/files
  - new: https://git.openjdk.org/jfx/pull/1637/files/bbe492aa..26e7790b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1637&range=05
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1637&range=04-05

  Stats: 6 lines in 1 file changed: 3 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jfx/pull/1637.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1637/head:pull/1637

PR: https://git.openjdk.org/jfx/pull/1637