We were super inconsistent about this, with most "new" classes living in
the Ladybird namespace, while "old" ones were in the global namespace,
or even sitting in the Browser namespace.
In order to follow spec text to achieve this, we need to change the
underlying representation of a host in AK::URL to deserialized format.
Before this, we were parsing the host and then immediately serializing
it again.
Making that change resulted in a whole bunch of fallout.
After this change, callers can access the serialized data through
this concept-host-serializer. The functional end result of this
change is that IPv6 hosts are now correctly serialized to be
surrounded with '[' and ']'.
This patch replaces the usage of QPalette::PlaceholderText with
QPalette::Text with opacity reduced to roughly 50%. This fixes the non
highlighted spans having an extremely low contrast compared to the
background in dark mode.
