radv: avoid context rolls when binding graphics pipelines

radv: avoid context rolls when binding graphics pipelines

It's common in some applications to bind a new graphics pipeline without
ending up changing any context registers.

This has a pipline have two command buffers: one for setting context
registers and one for everything else. The context register command buffer
is only emitted if it differs from the previous pipeline's.

v2: ensure late scissor emission is done when radv_emit_rbplus_state() is
    called
v2: make use of cmd_buffer->state.workaround_scissor_bug
v3: rename "workaround_scissor_bug" to
    "context_roll_without_scissor_emitted"

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>