Once upon a time, Wireshark could use GNU ADNS instead of c-ares
for asynchronous DNS lookups. GNU ADNS didn't check the system
hosts file (see 51984de040), so
we added the system hosts file using the same mechanism as profile
paths when using ADNS.
This was then confusing, because "use external DNS resolver / use
system DNS resolving" could be off but /etc/hosts was still used,
so the "only use profile hosts" option was created to avoid using
external system DNS hostsnames at all.
c-ares (and, for that matter, libunbound) does read /etc/hosts, so
this option doesn't do its primary purpose anymore. All it usually
does now is keep any hosts file in the global profile from being used,
but we don't have any other name resolution options where there's a
pref not to use global profile data.
Even more confusingly, if the option is true, then the -H option
to tshark to give a hosts file on the command line doesn't work.
add_hosts_file checks the preference and then doesn't actually
read the file from the command line, which is surely never wanted.
Most people don't understand what the option means, despite the
tooltip, and assume that it means "only use the hosts file as a
source of name resolution data", not "when using hosts files as
a source of name resolution data, only use the one from the personal
profile and not any from the global profile, the tshark command line,
or any other source."
Just mark the option as obsolete.
Related to #11470
3173400167