RFR: 8271090: Missing API docs in scenegraph classes [v2]

[Ajit Ghaisas]

> This PR fixes javadoc warnings primarily in javafx.graphics module along with a remaining few in javafx.fxml, javafx.base and javafx.media modules.
> 
> Note :
> - The javadoc needs to be generated with the JDK 18 EA build.
> - There are still few remaining warnings in these modules. The root cause is different and they will be addressed under [JDK-8270996](https://bugs.openjdk.java.net/browse/JDK-8270996)

Ajit Ghaisas has updated the pull request incrementally with one additional commit since the last revision:

  8271090 - fix review comments

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

Changes:
  - all: https://git.openjdk.java.net/jfx/pull/650/files
  - new: https://git.openjdk.java.net/jfx/pull/650/files/239c0634..9ff692db

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jfx&pr=650&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jfx&pr=650&range=00-01

  Stats: 38 lines in 6 files changed: 21 ins; 12 del; 5 mod
  Patch: https://git.openjdk.java.net/jfx/pull/650.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/650/head:pull/650

PR: https://git.openjdk.java.net/jfx/pull/650