Post tag metabox

[brenoalvs]

• Investigate if we can modify the terms retrieved by this metabox. See if the metabox uses the get_terms function (we have a get_terms filter) or if we can use pre_get_terms.

The focus is filter the terms by language meta field as we do with post types.

If we can't modify the metabox we'll need remove it and create a clone with those filters.

[brenoalvs]

Since tag metabox uses AJAX to retrieve tags results, we'll need to create a custom metabox to support multilanguage tags.