Various fixes to the MySQL python commands

[aadant]

mysql_dumper.py

• support for partitioned tables only, without the --partitioned_table_only flag, tables and partitioned matching the regexps are dumped
• support for very large dump definitions with a lot of partitions
• all tables are selected by default (--include_tables_regex .)

mysql_parser.py

• python ANTLR translation skips the collation that can be found in generated column definitions.
• support for generated columns see Values of the generated columns in MySQL are not transfered to the ClickHouse table #459

sink-connector/python/db_compare/clickhouse_table_checksum.py

• added a max_datetime_value to even out sub-second discrepancies in the max datetimes (overflows)

[minguyen9988]

lgtm