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/include/begin_include_file.inc

@@ -0,0 +1,82 @@
+# ==== Purpose ====
+#
+# This is an auxiliary file that facilitates writing include/*.inc
+# files. It has three purposes:
+#
+#  1. Store mtr's state at the beginning of the .inc file and restore
+#     the state at the end. The following status is restored:
+#
+#     disable_warnings
+#     disable_query_log
+#     disable_result_log
+#     disable_abort_on_errors
+#     Current connection
+#
+#  2. This file also prints the name of the .inc file that sources
+#     it. Only the name of the top-level .inc file is printed: if
+#     file_1.inc sources file_2.inc, then this file only prints
+#     file_1.inc.
+#
+#  3.  If the mysqltest variable $rpl_debug is set, then
+#      this file will print:
+#
+#        ==== BEGIN include/<filename> ====
+#
+#      and end_include_file.inc will print
+#
+#        ==== END include/<filename> ====
+#
+#      These printouts are indented to make it easier to read the
+#      result log.
+#
+#
+# ==== Usage ====
+#
+# # At the beginning of include/my_file.inc:
+# --let $include_filename= my_file.inc
+# [--let $rpl_debug= 1]
+# --source include/begin_include_file.inc
+#
+# # At the end of include/my_file.inc:
+# --let $include_filename= my_file.inc
+# --source include/end_include_file.inc
+#
+# Parameters:
+#   $include_filename
+#     The basename of the file: a file named /path/to/my_file.inc
+#     should set $include_filename=my_file.inc.  This parameter
+#     must be provided both for begin_include_file.inc and
+#     end_include_file.inc.
+#
+#   $rpl_debug
+#     If set, this script will print the following text:
+#      ==== BEGIN include/$include_filename.inc ====
+
+
+# Print 'include/$include_filename', but only when invoked from
+# the top-level. We don't want to print
+# 'include/$include_filename' from all files included
+# recursively.
+if (!$_include_file_depth)
+{
+  --echo include/$include_filename
+}
+--inc $_include_file_depth
+if ($rpl_debug)
+{
+  --echo $_include_file_indent==== BEGIN include/$include_filename ====
+}
+
+--let $_include_file_enabled_warnings= $ENABLED_WARNINGS$_include_file_enabled_warnings
+--let $_include_file_enabled_query_log= $ENABLED_QUERY_LOG$_include_file_enabled_query_log
+--let $_include_file_enabled_result_log= $ENABLED_RESULT_LOG$_include_file_enabled_result_log
+--let $_include_file_enabled_abort_on_error= $ENABLED_ABORT_ON_ERROR$_include_file_enabled_abort_on_error
+--let $_include_file_connection= $CURRENT_CONNECTION,$_include_file_connection
+
+if ($rpl_debug)
+{
+  --echo $_include_file_indent con='$CURRENT_CONNECTION' warn='$ENABLED_WARNINGS' qlog='$ENABLED_QUERY_LOG' rlog='$ENABLED_RESULT_LOG' aborterr='$ENABLED_ABORT_ON_ERROR'
+}
+
+--let $include_filename=
+--let $_include_file_indent= .$_include_file_indent