This PR fixes same issue as MDEV-21577 for TRUNCATE TABLE.
MDEV-21577 fixed TOI replication for OPTIMIZE, REPAIR and ALTER TABLE
operating on FK child table. It was later found out that also TRUNCATE
has similar problem and needs a fix.

The actual fix is to do FK parent table lookup before TRUNCATE TOI
isolation and append found FK parent table names in certification key
list for the write set.

PR contains also new test scenario in galera_ddl_fk_conflict test where
FK child has two FK parent tables and there are two DML transactions operating
on both parent tables.

For development convenience, new TO isolation macro was added:
WSREP_TO_ISOLATION_BEGIN_IF and WSREP_TO_ISOLATION_BEGIN_ALTER macro was changed
to skip the goto statement.
Reviewed-by: Jan Lindström <jan.lindstrom@mariadb.com>