Add test of d7 term localized source plugin

Yay thanks!

Verified that the isNotNull() was superfluous because the code continues to inner join on locales target and a null value will never satisfy that inner join.

    // Add in the property, which is either name or description.
    // Cast td.tid as char for PostgreSQL compatibility.
    $query->leftJoin('i18n_string', 'i18n', 'CAST(td.tid AS CHAR(255)) = i18n.objectid');
    $query->condition('i18n.type', 'term');
    $query->isNotNull('i18n.lid');
    $query->addField('i18n', 'lid');
    $query->addField('i18n', 'property');

    // Add in the translation for the property.
    $query->innerJoin('locales_target', 'lt', 'i18n.lid = lt.lid');
    $query->addField('lt', 'language', 'lt.language');
    $query->addField('lt', 'translation');

Committed 6f1111f and pushed to 8.8.x. Thanks!