RFR: 8275911: Keyboard doesn't show when tapping inside an iOS text input control

[Jose Pereda]

After [JDK-8245053](https://bugs.openjdk.java.net/browse/JDK-8245053) for Android, this PR applies the same approach on iOS: tapping on a text input control on iOS shows the keyboard, which hides after the control loses the focus. 

Now, both platforms have the same behaviour.

Tested on an iOS device.

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Commit messages:
 - Show iOS keyboard when user taps on TextInput controls

Changes: https://git.openjdk.java.net/jfx/pull/653/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx&pr=653&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8275911
  Stats: 90 lines in 2 files changed: 60 ins; 2 del; 28 mod
  Patch: https://git.openjdk.java.net/jfx/pull/653.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/653/head:pull/653

PR: https://git.openjdk.java.net/jfx/pull/653