Only allow system and graphics to create secure displays

Previously, we allowed any process that had the permission
ACCESS_SURFACE_FLINGER to create a display, either secure or
not secure. The shell process needs this permission to create
a display for screen recording. However, we just shouldn't allow
any process to create a secure display since that would allow
them to render secure content. Instead, only allow system
and graphics to create secure displays.

Fixes: 154721930
Test: Modified screenrecord to create secure display, which fails
Test: SurfaceFlinger_test
Test: SurfaceInterceptorTest
Test: DisplayTransactionTest
Change-Id: Ib3c5b6c8abd41f3f6fc6a71273cb2a17bfdba959