Adjustable Block Log Splitting and Pruning

Key points of this MR:

1. A wrapper to block_log class is introduced that encapsulates multi-file block log handling (also with pruning). The block_log_wrapper also serves as block_read_i implementation, i.e. it's a block reader during replay (replacing block_log_reader class).
2. Static methods of (de)compression have been moved outside block_log class to reduce including its header file.
3. Helper class block_log_file_name_info was added in block_log files. See its description.
4. Block-log-related fields of open_args have been separated into block_log_wrapper::block_log_open_args.
5. debug_push_blocks has been removed from debug_node_api.