patch 8.2.3765: Vim9: cannot use a lambda for 'opfunc' and others

Problem:    Vim9: cannot use a lambda for 'opfunc' and others.
Solution:   Convert the lambda to a string.
diff --git a/src/vim9.h b/src/vim9.h
index c82ba81..99b952f 100644
--- a/src/vim9.h
+++ b/src/vim9.h
@@ -55,7 +55,8 @@
     ISN_STORES,	    // pop into script variable isn_arg.loadstore
     ISN_STOREOUTER,  // pop variable into outer scope isn_arg.outer
     ISN_STORESCRIPT, // pop into script variable isn_arg.script
-    ISN_STOREOPT,    // pop into option isn_arg.string
+    ISN_STOREOPT,    // pop into option isn_arg.storeopt
+    ISN_STOREFUNCOPT, // pop into option isn_arg.storeopt
     ISN_STOREENV,    // pop into environment variable isn_arg.string
     ISN_STOREREG,    // pop into register isn_arg.number
     // ISN_STOREOTHER, // pop into other script variable isn_arg.other.
@@ -291,7 +292,7 @@
     varnumber_T	stnr_val;
 } storenr_T;
 
-// arguments to ISN_STOREOPT
+// arguments to ISN_STOREOPT and ISN_STOREFUNCOPT
 typedef struct {
     char_u	*so_name;
     int		so_flags;