RFR: 8310638: Filtering a TableView with a large number of items freezes the UI

[Johan Vos]

This PR fix a performance issue introduced by the fix for JDK-8306447. In that PR, we changed the behavior in case the cellcount changes. In case the cellcount changes to a lower value than the original one, we have to make sure the current index is not higher than the new amount of cells as that would lead to unnecessary computations.

Fix for JDK-8310638

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Commit messages:
 - In case the cellcount changes to a lower value, make sure the current index is not higher than

Changes: https://git.openjdk.org/jfx/pull/1163/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1163&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8310638
  Stats: 42 lines in 3 files changed: 41 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jfx/pull/1163.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1163/head:pull/1163

PR: https://git.openjdk.org/jfx/pull/1163