Missing TextField, TextArea, and SearchField text-input APIs

The desktop TextField, TextArea, and SearchField controls are missing common text-input APIs that are available in the underlying Avalonia TextBox control and expected by users coming from Xojo-style desktop controls.

Missing or incomplete surface area:

• TextField.KeyDown(key As String) and TextField.KeyUp(key As String)
• TextArea.KeyDown(key As String) and TextArea.KeyUp(key As String)
• SearchField.KeyDown(key As String) and SearchField.KeyUp(key As String)
• A maximum input length property, equivalent to Avalonia TextBox.MaxLength / Xojo MaximumCharactersAllowed
• A password-entry mode for TextField, equivalent to Avalonia TextBox.PasswordChar / Xojo Password
• Horizontal text alignment for text input controls, equivalent to Avalonia TextBox.TextAlignment

Expected behaviour: Objo desktop text-input controls should expose these APIs consistently in compile-time metadata, runtime native methods/properties, designer code generation, and documentation.