MDEV-36092 New-style hint: [NO_]SPLIT_MATERIALIZED

Support for optimizer hints NO_SPLIT_MATERIALIZED and
SPLIT_MATERIALIZED.  These hints allow fine-grained control
of the "lateral derived" optimization within a query.

Introduces new overload of hint_table_state function which
tells both a hint's value as well as whether it is present.
This is useful to disambiguate cases that the other version
of hint_table_state cannot, such as when a hint is forcing
a behavior in the optimizer that it would not normally do
and the corresponding optimizer switch is enabled.

sql/opt_hints.h

@@ -659,6 +659,14 @@ public:
 };
 
 
+enum class hint_state
+{
+  NOT_PRESENT,  // Hint is not specified
+  ENABLED,      // Hint is specified as enabled
+  DISABLED      // Hint is specified as disabled
+};
+
+
 /**
   Returns key hint value if hint is specified, returns
   optimizer switch value if hint is not specified.
@@ -706,6 +714,14 @@ bool hint_table_state(const THD *thd, const TABLE_LIST *table_list,
 bool hint_table_state(const THD *thd, const TABLE *table,
                       opt_hints_enum type_arg, bool fallback_value);
 
+
+/*
+  Similar to above but returns hint_state enum
+*/
+hint_state hint_table_state(const THD *thd,
+                            const TABLE_LIST *table_list,
+                            opt_hints_enum type_arg);
+
 #ifndef DBUG_OFF
 const char *dbug_print_hints(Opt_hints_qb *hint);
 #endif