Notify with `onIsInDesktopModeChanged()`

This CL renamed `onDesktopVisibilityChanged()` to
`onIsInDesktopModeChanged()` and adds a parameter for the display ID
on which the change is taking place.

When the multiple desktops flags are disabled, the behavior should
remain exactly as it is today; `onIsInDesktopModeChanged()` is
triggered only for the `DEFAULT_DISPLAY`, and when the same old
conditions occur.

Bug: 394685645
Test: m
Flag: com.android.window.flags.enable_multiple_desktops_frontend
Flag: com.android.window.flags.enable_multiple_desktops_backend
Change-Id: I31658b1b7932c787ebd430cee7e5c99bdd01e8c9