When changing position and/or size of the editor of a FindReplaceOverlay
while it is hidden, e.g., because another editor in the same editor
stack is active, the position and size of the overlay is not updated
accordingly. Thus, when making the editor of that overlay active again,
its position relative to the editor and size is still the same as before
another editor was set active, i.e., it is usually wrong.

With this change, the size and position of an overlay is always updated
upon resize operations of the target editor, even if the editor is not
visible.

Fixes https://github.com/eclipse-platform/eclipse.platform.ui/issues/2478