BUG#49978: Replication tests don't clean up replication state at the end

Major replication test framework cleanup. This does the following:
 - Ensure that all tests clean up the replication state when they
   finish, by making check-testcase check the output of SHOW SLAVE STATUS.
   This implies:
    - Slave must not be running after test finished. This is good
      because it removes the risk for sporadic errors in subsequent
      tests when a test forgets to sync correctly.
    - Slave SQL and IO errors must be cleared when test ends. This is
      good because we will notice if a test gets an unexpected error in
      the slave threads near the end.
    - We no longer have to clean up before a test starts.
 - Ensure that all tests that wait for an error in one of the slave
   threads waits for a specific error. It is no longer possible to
   source wait_for_slave_[sql|io]_to_stop.inc when there is an error
   in one of the slave threads. This is good because:
    - If a test expects an error but there is a bug that causes
      another error to happen, or if it stops the slave thread without
      an error, then we will notice.
    - When developing tests, wait_for_*_to_[start|stop].inc will fail
      immediately if there is an error in the relevant slave thread.
      Before this patch, we had to wait for the timeout.
 - Remove duplicated and repeated code for setting up unusual replication
   topologies. Now, there is a single file that is capable of setting
   up arbitrary topologies (include/rpl_init.inc, but
   include/master-slave.inc is still available for the most common
   topology). Tests can now end with include/rpl_end.inc, which will clean
   up correctly no matter what topology is used. The topology can be
   changed with include/rpl_change_topology.inc.
 - Improved debug information when tests fail. This includes:
    - debug info is printed on all servers configured by include/rpl_init.inc
    - User can set $rpl_debug=1, which makes auxiliary replication files
      print relevant debug info.
 - Improved documentation for all auxiliary replication files. Now they
   describe purpose, usage, parameters, and side effects.
 - Many small code cleanups:
    - Made have_innodb.inc output a sensible error message.
    - Moved contents of rpl000017-slave.sh into rpl000017.test
    - Added mysqltest variables that expose the current state of
      disable_warnings/enable_warnings and friends.
    - Too many to list here: see per-file comments for details.

mysql-test/suite/rpl/t/rpl_init_slave_errors.test

@@ -53,10 +53,11 @@ start slave;
 # slave is going to stop because of emulated failures
 # but there won't be any crashes nor asserts hit.
 #
-source include/wait_for_slave_to_stop.inc;
+# 1593 = ER_SLAVE_FATAL_ERROR
+--let $slave_sql_errno= 1593
+--let $show_slave_sql_error= 1
+--source include/wait_for_slave_sql_error.inc
 
-let $error= query_get_value(SHOW SLAVE STATUS, Last_Error, 1);
-echo Reporting the following error: $error;
 call mtr.add_suppression("Failed during slave I/O thread initialization");
 
 SET GLOBAL debug= "";
@@ -66,22 +67,23 @@ SET GLOBAL debug= "";
 ######################################################################
 connection slave;
 
---disable_warnings
-stop slave;
---enable_warnings
-source include/wait_for_slave_to_stop.inc;
-
 reset slave;
 
 SET GLOBAL init_slave= "garbage";
 
 start slave;
-source include/wait_for_slave_sql_to_stop.inc;
-
-let $error= query_get_value(SHOW SLAVE STATUS, Last_Error, 1);
-echo Reporting the following error: $error;
+# 1064 = ER_PARSE_ERROR
+--let $slave_sql_errno= 1064
+--let $show_slave_sql_error= 1
+--source include/wait_for_slave_sql_error.inc
 
 ######################################################################
 #                             Clean up
 ######################################################################
 SET GLOBAL init_slave= "";
+
+# Clean up Last_SQL_Error
+--source include/stop_slave_io.inc
+RESET SLAVE;
+--let $rpl_only_running_threads= 1
+--source include/rpl_end.inc