Backwards incompatibility of TREXIO_TEXT back end

[q-posev]

TEXT back end relies on reading the entire group before each I/O operation (for sync-ing). The group is read from the .txt file in a particular order, according to trex.json. Thus, addition of a new attribute to a group changes the source code of the generated trexio_text_read_[group] function. As a result, the group produced before addition of an attribute cannot be read in the updated version of TREXIO.