class PresentView

Presents the view described by `view_spec`.

If `view_controller_request` is provided, it will be connected to a `ViewController`

implemented by the `GraphicalPresenter` server. When the view is dismissed,

the `ViewController` channel is closed with a `ZX_OK`, at which point it is safe

to clean up resources backing the view. To dismiss the view, the client should

call `ViewController.Dismiss()` and wait for the `ZX_OK` epitaph.

Not providing a `view_controller_request` handle will make it impossible for the

client to observe the view's lifecycle.

+ `view_spec` describes the view to present

+ `annotation_controller` a handle to an `AnnotationController`, allowing the

`GraphicalPresenter` server to observe and update the view's annotations.

+ `view_controller_request` an optional request for a controller for the view

* error `view_spec` must contain `view_holder_token` and `view_ref` for Gfx views,

OR `viewport_creation_token` for Flatland views, but never both. If both are

set, error `PresentViewError.INVALID_ARGS` is returned.

* error `PresentViewError.INVALID_ARGS` if `spec.view_holder_token` or

`spec.view_ref` are missing or invalid.