allow random_bytes() in virtual columns

mysql-test/suite/gcol/inc/gcol_blocked_sql_funcs_main.inc

@@ -257,9 +257,13 @@ drop table t1;
 --echo #
 
 create table t1 (a int);
---error ER_GENERATED_COLUMN_FUNCTION_IS_NOT_ALLOWED
+insert t1 values (1);
 alter table t1 add column b binary(32) generated always as (random_bytes(a));
-alter table t1 add column b binary(32) default (random_bytes(a));
+select a,length(b) from t1;
+--error ER_GENERATED_COLUMN_FUNCTION_IS_NOT_ALLOWED
+alter table t1 add index (b);
+alter table t1 add column c binary(32) default (random_bytes(a));
+select a,length(b),length(c) from t1;
 drop table t1;
 
 --echo #

mysql-test/suite/gcol/r/gcol_blocked_sql_funcs_innodb.result

@@ -177,9 +177,17 @@ drop table t1;
 # MDEV-29029 Index corruption and/or assertion failure upon using RANDOM_BYTES for indexed virtual column
 #
 create table t1 (a int);
+insert t1 values (1);
 alter table t1 add column b binary(32) generated always as (random_bytes(a));
+select a,length(b) from t1;
+a	length(b)
+1	32
+alter table t1 add index (b);
 ERROR HY000: Function or expression 'random_bytes()' cannot be used in the GENERATED ALWAYS AS clause of `b`
-alter table t1 add column b binary(32) default (random_bytes(a));
+alter table t1 add column c binary(32) default (random_bytes(a));
+select a,length(b),length(c) from t1;
+a	length(b)	length(c)
+1	32	32
 drop table t1;
 #
 #

mysql-test/suite/gcol/r/gcol_blocked_sql_funcs_myisam.result

@@ -179,9 +179,17 @@ drop table t1;
 # MDEV-29029 Index corruption and/or assertion failure upon using RANDOM_BYTES for indexed virtual column
 #
 create table t1 (a int);
+insert t1 values (1);
 alter table t1 add column b binary(32) generated always as (random_bytes(a));
+select a,length(b) from t1;
+a	length(b)
+1	32
+alter table t1 add index (b);
 ERROR HY000: Function or expression 'random_bytes()' cannot be used in the GENERATED ALWAYS AS clause of `b`
-alter table t1 add column b binary(32) default (random_bytes(a));
+alter table t1 add column c binary(32) default (random_bytes(a));
+select a,length(b),length(c) from t1;
+a	length(b)	length(c)
+1	32	32
 drop table t1;
 #
 #

sql/item_strfunc.h

@@ -423,8 +423,7 @@ class Item_func_random_bytes : public Item_str_func
   }
   bool check_vcol_func_processor(void *arg) override
   {
-    return mark_unsupported_function(func_name(), "()", arg,
-                                     VCOL_NON_DETERMINISTIC | VCOL_NEXTVAL);
+    return mark_unsupported_function(func_name(), "()", arg, VCOL_NON_DETERMINISTIC);
   }
   Item *get_copy(THD *thd) override
   {