MDEV-30987 main.alter_table_online times out with view-protocol

disabie view-protocol for certain places:
1. While a transaction is in progress: a view gets locked for a
transaction duration, so DROP VIEW from a servicing conneciton
deadlocks. We can't just disable servicing connection, as
CREATE VIEW and DROP VIEW commit implicitly.
2. For querying Opened_table_definitions: the actual query executed
is `SELECT * FROM mysqltest_tmp_v`, then the view is dropped

mysql-test/main/alter_table_online_debug.test

@@ -61,9 +61,11 @@ set debug_sync= 'now SIGNAL end';
 --connection con2
 commit;
 --connection default
+--disable_view_protocol
 select variable_value into @otd from information_schema.session_status where variable_name='Opened_table_definitions';
 select * from t1;
 select variable_value-@otd from information_schema.session_status where variable_name='Opened_table_definitions';
+--enable_view_protocol
 
 --echo # long transaction and add column
 create or replace table t1 (a int);
@@ -693,6 +695,7 @@ alter table t1 add b int NULL, algorithm= copy, lock= none;
 --connection con2
 --reap
 update t1 set a= 222 where a = 2;
+--disable_view_protocol
 savepoint whoopsie;
 update t1 set a= 123 where a = 1;
 insert t3 values (2);
@@ -702,6 +705,7 @@ rollback to savepoint whoopsie;
 select * from t1;
 select * from t3;
 commit;
+--enable_view_protocol
 
 set debug_sync= 'now SIGNAL end';