xProfile fields meta data is not deleted when field is deleted

[slaFFik]

Example:
1) create a custom field (no matter in which fields group, even default one)
2) set its custom visibility, force visibility, required metas
3) check DB - records in wp_bp_xprofile_meta table are created for this new field
4) delete this field using standard BP functionality (on this page /wp-admin/users.php?page=bp-profile-setup click Delete for this new field)
5) check DB - field is deleted, metas - are not.

Same behavior when using directly built-in functions and methods, like BP_XProfile_Field::delete() etc.

[r-a-y]

Duplicate of #6658.