Due to recent changes to libxml2 (between 2.9.14 and 2.10.4,
See https://gitlab.gnome.org/GNOME/libxml2/-/issues/508), the
HTML parser doesn't take into account the namespaces (xmlns).
Because HTML shouldn't contain namespaces anyway, there is no
reason for use to keep using it. But switching to the XML
parser means that we have to pass the namespaces to every
single 'xpath_node(s)' method for it to be able to properly
navigate the XML structure.
Cherry picked from ui overhaul branch with a few modifications:
- channel folder is renamed to channels
- parsing for channel home and featured channels are removed due to
lack of infrastructure from other commits
(cherry picked from commit 44d18b8e147b47ad06a54cc6fd08423d9f39074d)