[ios] Add opt-in inline prediction text input support (#183650)

Expose inline prediction configuration through Flutter text fields so
apps can explicitly control iOS 17 inline predictive text behavior and
ensure the engine handles attributed marked text correctly.

This PR adds an `enableInlinePrediction` option to
`TextInputConfiguration`, `EditableText`, `TextField`, and
`CupertinoTextField`, and forwards that setting to the iOS text input
plugin.

On the engine side, the iOS text input implementation now:
- maps `enableInlinePrediction` to `UITextInlinePredictionType` on iOS
17+
- defaults inline prediction to disabled unless the framework explicitly
enables it
- handles `setAttributedMarkedText:selectedRange:` by forwarding the
plain string to the existing marked text flow so inline predictive text
updates are processed correctly

This keeps the feature opt-in, preserves existing behavior by default,
and gives apps explicit control over inline predictive text on supported
iOS versions.

Fixes: #135221

Previous PR: https://github.com/flutter/flutter/pull/182728

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Fixes] where supported.
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---------

Co-authored-by: Loïc Sharma <737941+loic-sharma@users.noreply.github.com>