Added takeScreenshot API to WindowOrganizer

Added requests to take screenshot of a Window that's organized
by the client. The resulting screenshot will be attached to a
SurfaceControl and reparented to the requested window's parent. The
client will be responsible for showing, setting z order, etc. They can
also re-parent to another place in the hierarchy. The default is to
parent to the window's parent since that's usually where a screenshot is
placed.

Test: Builds
Bug: 152114574
Change-Id: I5c829e029f3528fdb382842e9f0474097e01cb2e
Merged-In: I5c829e029f3528fdb382842e9f0474097e01cb2e