RFR: 8187474: Tree-/TableCell, TreeCell: editingCell/Item not updated in cell.startEdit

[Jeanette Winzenburg]

cell startEdit is supposed to update the editing location on its associated control - was done in ListCell, not in Tree-/TableCell nor TreeCell.

Fix was to add control.edit(..). Note that ListCell was also touched to use the exact same method call pattern as the fixed cell types.

Added/unignored cell tests that are failing/passing before/after the fix.

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Commit messages:
 - 8187474: Tree-/TableCell, TreeCell: editingCell/Item not updated in

Changes: https://git.openjdk.java.net/jfx/pull/638/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx&pr=638&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8187474
  Stats: 76 lines in 7 files changed: 46 ins; 21 del; 9 mod
  Patch: https://git.openjdk.java.net/jfx/pull/638.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/638/head:pull/638

PR: https://git.openjdk.java.net/jfx/pull/638