Upgrade SDK requirements, enhance input handling, and fix Windows PlatformException

[Ayad-Ben-Saliem]

This PR introduces updates to modernize the package, including SDK bumps, API signature updates, and improved keyboard interaction logic. Crucially, it fixes a PlatformException that occurred on Flutter Windows applications running on Flutter versions > 3.29.

Key Changes

SDK Upgrades:

• Bumped package SDK constraint to >=2.17.0.
• Updated example project SDK constraint to >=3.0.0.

API Updates:

• Updated chipBuilder and suggestionBuilder signatures to include an index parameter.
• Added an onSubmit callback.
• Updated constructors to use super.key and exposed TextCursorState.

Input & Keyboard Logic:

• Updated TextInputClient implementation to support viewId and missing interface methods.
• Implemented KeyboardListener for better handling of Backspace (chip deletion) and Tab (submit) keys.

Tests:

• Updated test suites to accommodate the new builder signatures.◦