audio r_submix: Suggest configuration from the peer

When there is a pipe established for a remote submix
device, suggest the configuration of the peer when opening
the other end.

Refactor SubmixRoute management to move it out from
StreamRemoteSubmix so that ModuleRemoteSubmix could also
use it.

Bug: 294962274
Test: atest audiorouting_tests
Change-Id: Ib31a662e7b65b92c614dc441a01160cae3485f3a