Add the ability to set up SOCKS or HTTP Proxy prior to logging into a remote service

### Is your feature request related to a problem? Please describe.

I host a NextCloud instance as an I2P Service which is not easily accessible until the client is configured to use a proxy, usually an HTTP Proxy on port 4444. Currently, the proxy settings are not available until after the user has connected to a service. This means that it's impossible to use an Android client with a NextCloud instance that operates only as an I2P Service. A similar issue would exist for Tor clients who want to connect to NextCloud as an Onion service.

### Describe the solution you'd like

I would like to have a menu which enables the user to configure a SOCKS5 or HTTP proxy before attempting to connect to a NextCloud instance.

### Describe alternatives you've considered

It's possible to build point-to-point connections in I2P which will present the remote NextCloud instance as if it were on the localhost. However, this process is cumbersome and fails to be dynamic enough to accommodate NextCloud instances across many `.i2p` hosts. It is even more cumbersome to attempt this with Orbot.