RFR: 8334900: IOOBE when adding data to a Series of a BarChart that already contains data [v4]

[Markus Mack]

> This PR is a fix for another IOOBE that I discovered while working on #1476.
> 
> The PR simplifies the code for adding a series that already contains data by adding the data points one-by-one.
> As far as I can see no attempt was previously made to optimize the bulk operation except for some trivial O(1) operations, so this should have no noticable performance impact.
> 
> Accidentally this fixes another bug related to the missing "negative" style class when negative data values are added.
> 
> Also, the PR aligns the handling of duplicate categories with the behavior clarified in #1476, when there are duplicates in the data that was already in the series before the series was added to the chart.
> 
> Note a change was made to the createTestSeries() test method, letting it start at index 1, avoiding the duplicate data items resulting from multiplying by 0.
> Without this change `testSeriesRemoveAnimatedStyleClasses` would fail because it counts the number of plot children, where the duplicates are now removed.

Markus Mack has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains six commits:

 - test "negative" style class in BarChartTest tests
 - Merge remote-tracking branch 'refs/remotes/origin/master' into fixes/bar-chart-add-nonempty-series
 - fix "negative" style class when series is changed
 - Merge remote-tracking branch 'refs/remotes/origin/master' into fixes/bar-chart-add-nonempty-series
   
   # Conflicts:
   #	modules/javafx.controls/src/test/java/test/javafx/scene/chart/BarChartTest.java
 - BarChart: Fix adding non-empty series
 - BarChart: Add styleClass "negative" for added data

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Changes: https://git.openjdk.org/jfx/pull/1488/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1488&range=03
  Stats: 125 lines in 2 files changed: 94 ins; 28 del; 3 mod
  Patch: https://git.openjdk.org/jfx/pull/1488.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1488/head:pull/1488

PR: https://git.openjdk.org/jfx/pull/1488