MDEV-14123: ".rocksdb folder may break workflow", and other MDEVs

Rename  Use '#rocksdb' instead of '.rocksdb' as subdirectory for RocksDB
datadir.

storage/rocksdb/ha_rocksdb.cc

@@ -1446,7 +1446,7 @@ static MYSQL_SYSVAR_UINT(
 static MYSQL_SYSVAR_STR(datadir, rocksdb_datadir,
                         PLUGIN_VAR_OPCMDARG | PLUGIN_VAR_READONLY,
                         "RocksDB data directory", nullptr, nullptr,
-                        "./.rocksdb");
+                        "./#rocksdb");
 
 static MYSQL_SYSVAR_STR(supported_compression_types,
   compression_types_val,

storage/rocksdb/mysql-test/rocksdb/suite.opt

---ignore-db-dirs=.rocksdb --plugin-load=$HA_ROCKSDB_SO --default-storage-engine=rocksdb
+--ignore-db-dirs=#rocksdb --plugin-load=$HA_ROCKSDB_SO --default-storage-engine=rocksdb
 

storage/rocksdb/mysql-test/rocksdb_sys_vars/suite.opt

---ignore-db-dirs=.rocksdb --plugin-load=$HA_ROCKSDB_SO
+--ignore-db-dirs=#rocksdb --plugin-load=$HA_ROCKSDB_SO
 

storage/rocksdb/mysql-test/storage_engine/parts/suite.opt

---ignore-db-dirs=.rocksdb --plugin-load=$HA_ROCKSDB_SO --binlog_format=ROW --loose-rocksdb_flush_log_at_trx_commit=0
+--ignore-db-dirs=#rocksdb --plugin-load=$HA_ROCKSDB_SO --binlog_format=ROW --loose-rocksdb_flush_log_at_trx_commit=0

storage/rocksdb/mysql-test/storage_engine/suite.opt

---ignore-db-dirs=.rocksdb --plugin-load=$HA_ROCKSDB_SO --binlog_format=ROW --collation-server=latin1_bin --loose-rocksdb_flush_log_at_trx_commit=0
+--ignore-db-dirs=#rocksdb --plugin-load=$HA_ROCKSDB_SO --binlog_format=ROW --collation-server=latin1_bin --loose-rocksdb_flush_log_at_trx_commit=0

storage/rocksdb/mysql-test/storage_engine/trx/suite.opt

---ignore-db-dirs=.rocksdb --plugin-load=$HA_ROCKSDB_SO --binlog_format=ROW --loose-rocksdb_flush_log_at_trx_commit=0
+--ignore-db-dirs=#rocksdb --plugin-load=$HA_ROCKSDB_SO --binlog_format=ROW --loose-rocksdb_flush_log_at_trx_commit=0