MDEV-30706 Different results of selects from view and CTE with same definition

MDEV-30668 Set function aggregated in outer select used in view definition

This patch fixes two bugs concerning views whose specifications contain
subqueries with set functions aggregated in outer selects.
Due to the first bug those such views that have implicit grouping were
considered as mergeable. This led to wrong result sets for selects from
these views.
Due to the second bug the aggregation select was determined incorrectly and
this led to bogus error messages.
The patch added several test cases for these two bugs and for four other
duplicate bugs.
The patch also enables view-protocol for many other test cases.

Approved by Oleksandr Byelkin <sanja@mariadb.com>

sql/sql_lex.h

@@ -1003,6 +1003,8 @@ public:
 
   bool set_lock_to_the_last_select(Lex_select_lock l);
 
+  bool can_be_merged();
+
   friend class st_select_lex;
 };