Make the HideSoftInputOnTappedChangedManager class public

[APopatanasov]

Description

I have a native control exposed in MAUI via a handler. The native control is a composite one and contains a child of type UITextField in iOS and EditText in Android. I want to take advantage of the HideSoftInputOnTapped property of the ContentPage and hide the keyboard when the parent page is tapped.

As the HideSoftInputOnTappedChangedManager class is internal I cannot use it and call its UpdateFocusForView method for my custom control.

Also, the UpdateFocusForView method only takes the MAUI View as a parameter and the logic in the method heavily depends on the fact the the platform view inherits either from UITextField or EditText. For native controls that has a child of UITextField/EditText that method cannot be used.

Public API Changes

Mark the HideSoftInputOnTappedChangedManager as public and provide a method through which you can pass the native control that contains UITextField/EditText whose keyboard should be hidden.

Intended Use-Case

I want my controls to respect the HideSoftInputOnTapped property of the ContentPage and hide its keyboard like the Entry control.

[APopatanasov]

Partially addressed with #19626.