desktop-exploded-view: WMShell change for activating a window from desktop task view

Clicking on one task window in the desktop exploded view, it should
activate that task window.

In this CL, we made changes to `IDesktopMode.aidl`'s two functions
`showDesktopApps` and `activateDesk` so that they accept an additional
`taskIdInFront` parameter, to bring both all desktop apps in a certain
desk and the new `taskIdInFront` to front.

Flag: com.android.launcher3.enable_desktop_exploded_view
Test: Manual
Bug: 353948437

Change-Id: I7c134f4bda976b4a09d956bd7aa0267d4a2619ad