This PR adds a new setting to the config: `network.timeout`. This setting
defines a time period during which all handshake procedures and
ceremonies must be completed. If not - connection is aborted. This
should help in situations when connection is established but client
cannot continue for some reason (for example, RST sent by some middle box).

go install github.com/dolonet/mtg-multi@latest was broken because go.mod
declared module path as github.com/9seconds/mtg/v2 while the repo lives
at github.com/dolonet/mtg-multi. Users ended up installing upstream
binary without multi-secret support.

Fixes https://github.com/9seconds/mtg/issues/376#issuecomment-4162877568