MDEV-27128: Implement JSON Schema Validation FUNCTION

Implementation:
Implementation is made according to json schema validation draft 2020

JSON schema basically has same structure as that of json object, consisting
of key-value pairs. So it can be parsed in the same manner as
any json object.

However, none of the keywords are mandatory, so making guess about the
json value type based only on the keywords would be incorrect.
Hence we need separate objects denoting each keyword.

So during create_object_and_handle_keyword() we create appropriate objects
based on the keywords and validate each of them individually on the json
document by calling respective validate() function if the type matches.
If any of them fails, return false, else return true.

sql/sql_parse.h

@@ -189,4 +189,20 @@ check_table_access(THD *thd, privilege_t requirements,TABLE_LIST *tables,
 { return false; }
 #endif /*NO_EMBEDDED_ACCESS_CHECKS*/
 
+
+/*
+  Allocating memory and *also* using it (reading and
+  writing from it) because some build instructions cause
+  compiler to optimize out stack_used_up. Since alloca()
+  here depends on stack_used_up, it doesnt get executed
+  correctly and causes json_debug_nonembedded to fail
+  ( --error ER_STACK_OVERRUN_NEED_MORE does not occur).
+*/
+#define ALLOCATE_MEM_ON_STACK(A) do \
+                              { \
+                                uchar *array= (uchar*)alloca(A); \
+                                bzero(array, A); \
+                                my_checksum(0, array, A); \
+                              } while(0)
+
 #endif /* SQL_PARSE_INCLUDED */