RFR: 8245499: Text input controls should show handles on iOS

[Jose Pereda]

After JDK-8242167, a JavaFX control is used for text input on iOS instead of the native control, on a touch enabled
device. However, selection handles are not enabled and currently text selection is not possible at all.

This PR enables handles on iOS as in the rest of the platforms with touch support.

It also tries to accommodate its style to the native style for handles, where selection handles have a circle shape and
are a little bit bigger, and there is no caret handle.

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Commit messages:
 - Use circular shape for selection handles on iOS
 - Don’t show caretHandle on iOS
 - Enable Show_Handles on iOS

Changes: https://git.openjdk.java.net/jfx/pull/231/files
 Webrev: https://webrevs.openjdk.java.net/jfx/231/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8245499
  Stats: 35 lines in 4 files changed: 18 ins; 2 del; 15 mod
  Patch: https://git.openjdk.java.net/jfx/pull/231.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/231/head:pull/231

PR: https://git.openjdk.java.net/jfx/pull/231