Make error messages from DROP TABLE and DROP TABLE IF EXISTS consistent

- IF EXISTS ends with a list of all not existing object, instead of a
  separate note for every not existing object
- Produce a "Note" for all wrongly dropped objects
  (like trying to do DROP SEQUENCE for a normal table)
- Do not write existing tables that could not be dropped to binlog

Other things:
MDEV-22820 Bogus "Unknown table" warnings produced upon attempt to drop
           parent table referenced by FK
This was caused by an older version of this commit patch and later fixed

mysql-test/main/alter_table.result

@@ -272,8 +272,7 @@ ERROR 42000: Incorrect table name ''
 drop table t1;
 drop table if exists t1, t2;
 Warnings:
-Note	1051	Unknown table 'test.t1'
-Note	1051	Unknown table 'test.t2'
+Note	1051	Unknown table 'test.t1,test.t2'
 create table t1 ( a varchar(10) not null primary key ) engine=myisam;
 create table t2 ( a varchar(10) not null primary key ) engine=merge union=(t1);
 flush tables;