Set limits on binlog size

[calind]

We should set the following variables with sensible defaults:

if PVC >= 2G:
    binlog_space_limit = 50% * PVC
    max_binlog_size = min(25% * `binlog_space_limit`, 1G)
else:
    max_allowed_packet = 4M
    binlog_space_limit = 33% * PVC
    max_binlog_size = min(33% * `binlog_space_limit`, 256M)

This takes into consideration:

• max_allowed_packet: 4MB in 5.7 and 64MB in 8.0
• max_binlog_size: no less than few max_allowed_packet (eg. 2x)
• binlog_space_limit: no less than few max_binlog_size (https://www.percona.com/doc/percona-server/5.7/flexibility/max_binlog_files.html#binlog_space_limit)

Considering the minimum requirements (max_binlog_size = 2 *max_allowed_packet, binlog_space_limit = 2 * max_binlog_size) there is at least a 256MB requirement for binlog.