handle native chain parties

[bekauz]

currently covenants assume that parties are interchain (non-neutron). this may not always be the case.

this will have impact on the inflow and outflow of funds from the covenant.

for inflows, we should skip the instantiation of ibc-forwarder for any native parties. the deposit address for that party will be the holder. lets combine this with using instantiate2 for the covenant instantiation flow as neutron will be launching it later this month.

for outflows, lets introduce the notion of native receivers on the interchain router. this is probably easiest by having an enum for both cases.

[bekauz]

updated description