patch 8.2.4216: Vim9: cannot use a function from an autoload import directly

Problem:    Vim9: cannot use a function from an autoload import directly.
Solution:   Add the AUTOLOAD instruction to figure out at runtime.
            (closes #9620)
diff --git a/src/proto/vim9instr.pro b/src/proto/vim9instr.pro
index 04ac89c..be41d7c 100644
--- a/src/proto/vim9instr.pro
+++ b/src/proto/vim9instr.pro
@@ -23,6 +23,7 @@
 int generate_PUSHJOB(cctx_T *cctx, job_T *job);
 int generate_PUSHBLOB(cctx_T *cctx, blob_T *blob);
 int generate_PUSHFUNC(cctx_T *cctx, char_u *name, type_T *type);
+int generate_AUTOLOAD(cctx_T *cctx, char_u *name, type_T *type);
 int generate_GETITEM(cctx_T *cctx, int index, int with_op);
 int generate_SLICE(cctx_T *cctx, int count);
 int generate_CHECKLEN(cctx_T *cctx, int min_len, int more_OK);