RFR: 8137244: Empty Tree/TableView with CONSTRAINED_RESIZE_POLICY is not properly resized

[Andy Goryachev]

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. Add data to the tree/table with a constrained resize policy
2. Clear the table
3. Try to resize the tree/table
Expected:
- the tree/table columns get resized
Observed:
- columns are not resized

Caused by an incomplete fix for RT-14855 / JDK-8113886

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Commit messages:
 - 8137244: cleanup
 - 8137244: constrained resize when empty

Changes: https://git.openjdk.org/jfx/pull/991/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=991&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8137244
  Stats: 111 lines in 5 files changed: 106 ins; 2 del; 3 mod
  Patch: https://git.openjdk.org/jfx/pull/991.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/991/head:pull/991

PR: https://git.openjdk.org/jfx/pull/991