This mainly helps our CI under valgrind, which starts a fresh instance
and immediately calls the invoice command. This can cause the topology
plugin to try to access the gossmap file before it's created.
We can also move the gossmap reading in topology to init time.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Invoices need to know what the peers' update contains, to create
routehints. It also wants to know if a peer has no other public
channels (so-called "dead end" peers) to eliminate them from routehint
consideration.
This was previously done by a special function to ask gossipd.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Temporarily rename old getroute to getrouteold (we will remove this).
Changelog-Changed: JSON-RPC: `getroute` is now implemented in a plugin.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
