SurfaceFlinger: Indicate whether we have captured secure layers.

For purposes of the screen rotation animation the system server is allowed
to capture secure (not protected) layers and trusted not to persist screenshots
which may contain secure layers. However when displaying the screen rotation animation,
the layer the screenshot is placed on will itself not be secure, so if we record
the animation the recording will contain persisted versions of the secure content. Here
we forward whether the screenshot contains secure content so that system server can do the right thing.

Bug: 69703445
Test: Transaction_test#SetFlagsSecureEuidSystem
Change-Id: I828cfe3faee3a0c84525f90b9df8b66e392bc240