RFR: 8088998: LineChart: duplicate child added exception when remove & add a series

[Karthik P K]

While checking for duplicate series addition to the line chart, `setToRemove` value was not considered before throwing exception. Hence code to handling the case of adding the removed series was never run.

Added condition to check `setToRemove` boolean value before throwing exception. Made changes to call `setChart` method after calling `seriesBeingRemovedIsAdded`. Otherwise chart will not be drawn for the series, only points will be plotted.

This issue is reproducible only when animation is enabled because timeline will be still running when removed series is added back to the same chart. Since timeline does not run in unit tests, added system test to validate the fix.

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Commit messages:
 - Fix linechart exception issue on adding removed series

Changes: https://git.openjdk.org/jfx/pull/1015/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1015&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8088998
  Stats: 138 lines in 2 files changed: 135 ins; 2 del; 1 mod
  Patch: https://git.openjdk.org/jfx/pull/1015.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/1015/head:pull/1015

PR: https://git.openjdk.org/jfx/pull/1015