Feature/cancel prompt with esc

[red-stronghold]

fixes #851
fixes #1392

• I have read the Contribution Guidelines
• I have commented on the issue above and discussed the intended changes
• A maintainer has signed off on the changes and the issue was assigned to me
• All newly added code is adequately covered by tests
• All existing tests are still running without errors
• The documentation was modified to reflect the changes OR no documentation changes are required.

Changes

For SelectionPrompt<T>:

• Allow setting a Func<T> property to be triggered on Cancel
• Extension methods to set the property, either with a Func or with a Value (for easier use)
• Capture 'ESC' key and cancel the prompt
• Return the specified result if the prompt is cancelled
• Unit tests to cover both extension methods.

For MultiSelectionPrompt<T>:

• Allow setting a Func<List<T>> property to be triggered on Cancel
• Extension methods to set the property, either with a Func, a List, a Value or an empty List (for easier use)
• Capture 'ESC' key and cancel the prompt
• Return the specified result if the prompt is cancelled
• Unit tests to cover all extension methods.

If property not set, the prompts works as before.

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