MDEV-9038 Binlog encryption tests

- created binlog_encryption test suite and added it to the default list
- moved some tests from rpl, binlog and multisource suites to extra
  so that they could be re-used in different suites
- made minor changes in include files

mysql-test/suite/binlog_encryption/rpl_loadfile.test

@@ -0,0 +1,11 @@
+--source extra/rpl_tests/rpl_loadfile.inc
+
+--let $datadir= `SELECT @@datadir`
+
+--echo #
+--echo # Check that the loaded data is encrypted in the master binlog
+--echo #
+
+--let SEARCH_FILE=$datadir/master-bin.0*
+--let SEARCH_PATTERN= xxxxxxxxxxx
+--source include/search_pattern_in_file.inc