Nest the ircd link under modules/protocol/

The protocol link is a different kind of module from the service
pseudo-clients, so give it its own home: modules/inspircd ->
modules/protocol/inspircd. A future ircd link is a new crate alongside
it. Workspace member, dependency path, the crate's own api path, and the
docs are updated to match. No code change.

modules/protocol/inspircd/Cargo.toml

@@ -5,4 +5,4 @@ edition = "2021"
 description = "InspIRCd server-to-server protocol module for fedserv."
 
 [dependencies]
-fedserv-api = { path = "../../api" }
+fedserv-api = { path = "../../../api" }