patch 8.2.4270: generating nv_cmdidxs.h requires building Vim twice

Problem:    Generating nv_cmdidxs.h requires building Vim twice.
Solution:   Move the table into a separate file and use a separate executable
            to extract the command characters. (Ozaki Kiichi, closes #9669)
diff --git a/src/version.c b/src/version.c
index 87f3845..a8db110 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    4270,
+/**/
     4269,
 /**/
     4268,