Hide event handler methods from autocomplete

The code editor's autocomplete offers event handler methods as if they were ordinary callable members. For example, typing Me. inside a Window event lists Calendar1_DatePressed, Calendar1_DisplayDateChanged, and every other handler wired up on the Window's controls, alongside the Window's real members. The same handler names also appear in bare-name completion while typing anywhere in the Window's code.

Event handlers are managed by the designers' Events panels, not authored as regular methods, and users are not meant to call them. They should never be presented in autocomplete. Expected behaviour: completion lists only real members — controls, properties, user-authored methods, and the built-in API. As a Window accumulates controls and wired events, the current behaviour increasingly buries the useful members under handler noise.