Check that private subnets are excluded in the "Integrated" mode

This task requires cooperating with the server-side.

There are two options of excluding the local network in the IPSec case.

* First, we could set `excludeLocalNetworks` to `true` when configuring the connection. In this case, the tunnel should ignore the routes that it receives from the server-side.
* Second, they could be configured on the server-side.

In theory, we're currently using the second option. However, we received a couple of complaints that private subnets aren't excluded when using the Integrated mode.

Here's what we should do:

1. Check if it's excluded or not (try opening some intranet website when AdGuard VPN is enabled).
2. If it's not, try setting `excludeLocalNetworks` and see if we can control routes on the client side.
3. If we can control it on the client-side, we should do it this way as it allows us have client-specific routes.

Again, ideally, I'd prefer to have a low-level setting that controls excluded routes (like I explained here: https://github.com/AdguardTeam/AdGuardVPNForiOS/issues/151).