DesktopTasksController PendingIntent: Start as ONE_SHOT.

There is a strong possibility when a user tries to open new Chrome window via App Header, there is already an active Pending Intent that was started by the launcher (when the user opens Chrome after being in Desktop mode). If the PendingIntent is active, trying to start another one will simply re-use the active one. The Launcher intent has the flag FLAG_ACTIVITY_RESET_TASK_IF_NEEDED, which is problematic for New Window case since then it will see the current Chrome task and just not open anything new.

What we will do then is make all PendingIntent fire off as ONE_SHOT so that they do not persist.

Bug: 407125053
Test: Manual. Open Gmail, put in Desktop, open Chrome, try to open New Window - succeeds.
Flag: EXEMPT bugfix
Change-Id: I70edb0613f711b92d4ba03718b85e9fcca9938bd