Prior to this commit the stage was drawn separately for each logical
monitor. This allowed to draw different parts of the stage with
different transformations, e.g. with a different viewport to implement
HiDPI support.

Go even further and have one view per CRTC. This causes the stage to
e.g. draw two mirrored monitors twice, instead of using the same
framebuffer on both. This enables us to do two things: one is to support
tiled monitors and monitor mirroring using the EGLStreams backend; the
other is that it'll enable us to tie rendering directly to the CRTC it
will render for. It is also a requirement for rendering being affected
by CRTC state, such as gamma.

It'll be possible to still inhibit re-drawing of the same content
twice, but it should be implemented differently, so that it will still
be possible to implement features requiring the CRTC split.

!1042