Cleanup: split GPU_batch

Split out presets and utilities for creating batches.
These functions are quite specialized and not related to typical usage.

source/blender/gpu/GPU_batch_utils.h

@@ -0,0 +1,40 @@
+/*
+ * ***** BEGIN GPL LICENSE BLOCK *****
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * ***** END GPL LICENSE BLOCK *****
+ */
+
+#ifndef __GPU_BATCH_UTILS_H__
+#define __GPU_BATCH_UTILS_H__
+
+struct rctf;
+
+#include "BLI_compiler_attrs.h"
+#include "BLI_sys_types.h"
+
+/* gpu_batch_utils.c */
+struct Gwn_Batch *GPU_batch_tris_from_poly_2d_encoded(
+        const uchar *polys_flat, uint polys_flat_len, const struct rctf *rect
+        ) ATTR_WARN_UNUSED_RESULT ATTR_NONNULL(1);
+struct Gwn_Batch *GPU_batch_wire_from_poly_2d_encoded(
+        const uchar *polys_flat, uint polys_flat_len, const struct rctf *rect
+        ) ATTR_WARN_UNUSED_RESULT ATTR_NONNULL(1);
+
+/* Only use by draw manager. Use the presets function instead for interface. */
+struct Gwn_Batch *gpu_batch_sphere(int lat_res, int lon_res) ATTR_WARN_UNUSED_RESULT;
+
+#endif  /* __GPU_BATCH_UTILS_H__ */