remove final imports.h and imports.c bits

This moves the fi_types to a new mesa_private.h and removes the
imports.c file. The vast majority of this patch is just removing
pound includes of imports.h and fixing up the recursive includes.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Kristian H. Kristensen <hoegsberg@google.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3024>

src/mesa/main/shared.c

@@ -27,7 +27,7 @@
  * Shared-context state
  */
 
-#include "util/imports.h"
+
 #include "mtypes.h"
 #include "hash.h"
 #include "atifragshader.h"
@@ -330,7 +330,7 @@ delete_semaphore_object_cb(GLuint id, void *data, void *userData)
  *
  * \param ctx GL context.
  * \param shared shared state pointer.
- * 
+ *
  * Frees the display lists, the texture objects (calling the driver texture
  * deletion callback to free its private data) and the vertex programs, as well
  * as their hash tables.