st/vega: Overhaul renderer with renderer states.

st/vega: Overhaul renderer with renderer states.

Renderer states are high-level states to perform specific tasks.  The
renderer is initially in INIT state.  In that state, the renderer is
used for OpenVG pipeline.

This commit adds a new COPY state to the renderer.  The state is used
for copying between two pipe resources using textured drawing.  It can
be used for vgCopyImage, for example.

Rather than modifying every user of the renderer, this commit instead
modifies renderer_copy_texture to use the COPY state internally.