This is not the main reason for the specific output in #9994. These ones are
more probably because of similar usage in GTK (which updated its own calls to
g_file_info_get_is_hidden|backup() in version 3.24.38). But we should likely
also update the various calls we have to use the generic
g_file_info_get_attribute_*() variants.

To be fair, it is unclear to me when we can be sure that an attribute is set.
For instance, when we call g_file_enumerate_children() or g_file_query_info()
with specific attributes, docs say that it is still possible for these
attributes to not be set. So I assume it means we should never use direct
accessor functions.

The only exception is that I didn't remove usage of g_file_info_get_name(),
since its docs says:

> * Gets a display name for a file. This is guaranteed to always be set.

Even though it also says just after:

> * It is an error to call this if the #GFileInfo does not contain
> * %G_FILE_ATTRIBUTE_STANDARD_DISPLAY_NAME.

Which is very contradictory. But assuming that this error warning was
over-zealous documentation, I kept the direct accessors since they are supposed
to be slightly more optimized (still according to in-code documentation) so
let's priorize them when we know they are set for sure.