RFR: 8207333: [Linux, macOS] Column sorting is triggered always after context menu request on table header [v3]

[Jose Pereda]

> Note: The JBS issue [JDK-8207333](https://bugs.openjdk.org/browse/JDK-8207333) refers to Linux, but it happens on macOS too. 
> 
> When a TableColumn has a ContextMenu, if the user right clicks on the tableColumnHeader, the ContextMenu shows up, but, as described on the issue, on macOS and Linux, the table gets sorted as well.
> 
> Currently, `TableColumnHeader#mouseReleasedHandler` checks for `MouseEvent::isPopupTriggered`, but it doesn't have a check on `mousePressed`. However,  it can be seen that a right click on the header has the following values for `MouseEvent:: isPopupTriggered` on the different platforms and mouse pressed and released events:
> 
> | isPopupTriggered on: | Windows  | macOS | Linux |
> | ------------- | ------------- | ------------- | ------------- |
> | mousePressed  | false  | true | true |
> | mouseReleased  | true  | false | false |
> 
> Also, the JavaDoc for `MouseEvent::isPopupTriggered` clearly states that:
> 
>> **Note**: Popup menus are triggered differently on different systems. Therefore, `popupTrigger` should be checked in both `onMousePressed` and `mouseReleased` for proper cross-platform functionality.
> 
> Therefore, this PR adds a check to `MouseEvent::isPopupTrigger` in the mouse pressed event, that can be used later on to cancel the header sorting when the mouse released event happens.
> 
> Also a system test has been added. It fails on macOS and Linux, and passes on Windows before this PR, and passes on the three platforms with this PR.

Jose Pereda has updated the pull request incrementally with one additional commit since the last revision:

  keep column drag lock

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

Changes:
  - all: https://git.openjdk.org/jfx/pull/1754/files
  - new: https://git.openjdk.org/jfx/pull/1754/files/561fcf18..526eb88b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1754&range=02
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1754&range=01-02

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jfx/pull/1754.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1754/head:pull/1754

PR: https://git.openjdk.org/jfx/pull/1754