The --skip-write-binlog message was confusing that it only had
an effect if the galera was enabled. There are uses beyond galera
so we apply SET SESSION SQL_LOG_BIN=0 as implied by the option
without being conditional on the wsrep status.

Remove wsrep.mysql_tzinfo_to_sql_symlink{,_skip} tests as they offered
no additional coverage beyond main.mysql_tzinfo_to_sql_symlink as no
server testing was done.

Introduced a variant of the galera.mariadb_tzinfo_to_sql as
galera.mysql_tzinfo_to_sql, which does testing using the mysql client
rather than directly importing into the server via mysqltest.

Update man page and mysql_tzinfo_to_sql to having a --skip-write-binlog
option.

merge notes:
10.4:
- conflicts in tztime.cc can revert to this version of --help text.
- tztime.cc - merge execute immediate @prep1, and leave %s%s trunc_tables, lock_tables
  after that.
10.6:
- Need to remove the not_embedded.inc in mysql_tzinfo_to_sql.test and
  replace it with no_protocol.inc
- leave both mysql_tzinfo_to_sql.test and mariadb_tzinfo_to_sql.sql
  tests.
- sql/tztime.cc - keep entirely 10.6 version.