Fixes #30779 - Implement ActionDispatch::RemoteIp (#7960)

The ActionDispatch::RemoteIp middleware can provide the remote IP
correctly as a property of the request object. This looks at
X-Forwarded-For headers while stripping out reverse proxies and falls
back to REMOTE_ADDR.

It has an option to provide a list of trusted reverse proxies which
needs to be exposed to the user. This option is exposed via a setting
which the installer can set. It needs to be in settings.yaml since
middleware can't dynamically reload config.

This middleware is enabled by default in Rails, which is an odd choice
because it actually opens up a security risk, as noted in its
documentation. Technically the best choice would be to disable the
middleware if running without a reverse proxy (like with Passenger).

It should also be noted that while there appears to be spoofing
protection inside the middleware, it doesn't actually work since the
Client-Ip is never set in our deployments.

This commit also consistently uses request.remote_ip to obtain the IP.

After this change, the remote_addr setting is no longer needed and also
no longer makes sense.

Co-authored-by: Marek Hulán <mhulan@redhat.com>

Co-authored-by: Marek Hulán <mhulan@redhat.com>