Change default ListenIp of Http server to 0.0.0.0

Change default ListenIp of Http server to 0.0.0.0

We see that a lot of support tickets are caused by this default setting,
as it is one of the things that blocks connections to the server with no
obvious indication that this is happening. To make it easier for first
time users to set up Impostor, it is important that this setting is
changed.

Previously we also recommended against direct exposing due to security
reasons, but I believe this fear to be unfounded: Microsoft claims that
the Kestrel server is hardened against web server vulnerabilities and
supports its use both with and without a reverse proxy.[1]

We still recommend using reverse proxies if HTTPS support is needed, so
that section of documentation still remains. Setting the ListenIp to
127.0.0.1 is still recommended when using a reverse proxy to remove the
ability for people to connect directly, so we add it there as a recommendation.

[1]: https://learn.microsoft.com/en-us/aspnet/core/fundamentals/servers/kestrel/when-to-use-a-reverse-proxy?view=aspnetcore-8.0