RFR: JDK-8325798: Spinner throws uncatchable exception on tab out from garbled text

[Marius Hanl]

When a `Spinner` is configured with e.g. Integers (`IntegerSpinnerValueFactory`) and the user types in a `String`, e.g. 'abc' and focuses another `Node`, an exception is thrown (`NumberFormatException`).
This exception is literally uncatchable, as it happens on focus lost.

The issue is the same as for the `DatePicker` component described in [JDK-8303478](https://bugs.openjdk.org/browse/JDK-8303478), which was fixed in PR: https://github.com/openjdk/jfx/pull/1274.

I did the exact same fix in this PR. Also added the same test.

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Commit messages:
 - JDK-8325798: Spinner throws uncatchable exception on tab out from garbled text

Changes: https://git.openjdk.org/jfx/pull/1365/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1365&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8325798
  Stats: 42 lines in 2 files changed: 39 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jfx/pull/1365.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1365/head:pull/1365

PR: https://git.openjdk.org/jfx/pull/1365