CancelAllDialogs mechanism in Skills CoreBot

[axelsrz]

The current behavior for Skill Core Bot considers cancelling all dialogs bottom-up, C# does provide this mechanism due to changes done for adaptive (DialogContainers, Dialog.Child property, CancelAllDialogsAsync bottom up, etc), but neither Python nor JS have ported those changes yet.

We should make a decision regarding what pattern to show in the samples to address this scenario in the missing languages.

[stevengum]

Moved this to R10 for triage discussions.

[gabog]

@axelsrz. @stevengum, what do we need to decide if we take this in R11 or not?

[axelsrz]

This change will ship with DialogManager changes