This commit restores defaults and functionality regarding binlogs
to the way it was prior to MDEV-27524. The mariabackup utility no
longer saves binlogs files as part of a backup without the --galera-info
option. However, since we use --galera-info during SST, the behavior
of mariabackup changes and, in combination with GTIDs support enabled,
mariabackup transfers one (most recent) binlog file obtained after
FLUSH BINARY LOGS. In other cases, binlogs are not transferred during
SST in mariabackup mode. As for SST in the rsync mode, it works the
same way as before MDEV-27524 - by default it transfers one last
binlog file.

The --sst-max-binlogs option for mariabackup and the sst_max_binlogs
parameter in the [sst] / server sections are no longer supported for
SST via mariabackup.