meson_options: implement disable-auth; delete pam

Implemented the disable-auth option.
This patch also removed the pam option which never worked.

Tested:
With disable-auth,

```
~# wget -qO- http://localhost/redfish/v1/Systems/
{
  "@odata.id": "/redfish/v1/Systems",
  "@odata.type": "#ComputerSystemCollection.ComputerSystemCollection",
  "Members": [
    {
      "@odata.id": "/redfish/v1/Systems/system"
    }
  ],
  "Members@odata.count": 1,
  "Name": "Computer System Collection"
}
```

Without disable-auth,

```
~# wget -qO- http://localhost/redfish/
{
  "v1": "/redfish/v1/"
}
~# wget -qO- http://localhost/redfish/v1/Systems/system
wget: server returned error: HTTP/1.1 401 Unauthorized
```

Signed-off-by: Nan Zhou <nanzhoumails@gmail.com>
Change-Id: I88e4e6fa6ed71096bc866b42b9af283645a65988
diff --git a/http/http_connection.hpp b/http/http_connection.hpp
index 4b4310f..fb5eac7 100644
--- a/http/http_connection.hpp
+++ b/http/http_connection.hpp
@@ -354,7 +354,7 @@
             completeRequest();
             return;
         }
-
+#ifndef BMCWEB_INSECURE_DISABLE_AUTHENTICATION
         if (!crow::authorization::isOnAllowlist(req->url, req->method()) &&
             thisReq.session == nullptr)
         {
@@ -365,7 +365,7 @@
             completeRequest();
             return;
         }
-
+#endif // BMCWEB_INSECURE_DISABLE_AUTHENTICATION
         res.setCompleteRequestHandler([self(shared_from_this())] {
             boost::asio::post(self->adaptor.get_executor(),
                               [self] { self->completeRequest(); });
@@ -566,7 +566,6 @@
                     return;
                 }
 
-                boost::beast::http::verb method = parser->get().method();
                 readClientIp();
 
                 boost::asio::ip::address ip;
@@ -575,8 +574,11 @@
                     BMCWEB_LOG_DEBUG << "Unable to get client IP";
                 }
                 sessionIsFromTransport = false;
+#ifndef BMCWEB_INSECURE_DISABLE_AUTHENTICATION
+                boost::beast::http::verb method = parser->get().method();
                 userSession = crow::authorization::authenticate(
                     ip, res, method, parser->get().base(), userSession);
+#endif // BMCWEB_INSECURE_DISABLE_AUTHENTICATION
                 bool loggedIn = userSession != nullptr;
                 if (loggedIn)
                 {