st/mesa: Add support for KHR_no_error flag

Add a new context flag and plumb it through the various layers of the
context creation code to set up dispatch tables for the no-error mode.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>

src/gallium/include/state_tracker/st_api.h

@@ -90,6 +90,7 @@ enum st_api_feature
 #define ST_CONTEXT_FLAG_FORWARD_COMPATIBLE  (1 << 1)
 #define ST_CONTEXT_FLAG_ROBUST_ACCESS       (1 << 2)
 #define ST_CONTEXT_FLAG_RESET_NOTIFICATION_ENABLED (1 << 3)
+#define ST_CONTEXT_FLAG_NO_ERROR            (1 << 4)
 
 /**
  * Reasons that context creation might fail.