RFR: 8154038: Spinner's converter should update its editor

[Karthik P K]

When converter was changed, `setText` method of spinner was not invoked to update the spinner text using new converter.

Added a listener to converter property of `SpinnerValueFactory` to call `setText` so that spinner text is updated using new converter.

Added unit test to validate the fix. Along with spinner of Double type, added a spinner of Integer type as well so that the fix is validated using 2 types of spinner.

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Commit messages:
 - Fix spinner converter issue

Changes: https://git.openjdk.org/jfx/pull/1057/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1057&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8154038
  Stats: 58 lines in 2 files changed: 58 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jfx/pull/1057.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/1057/head:pull/1057

PR: https://git.openjdk.org/jfx/pull/1057