Smash dkg into dkg, dkg-[recovery, promote, musig, pedpop]

promote and pedpop require dleq, which don't support no-std. All three should
be moved outside the Serai repository, per #597, as none are planned for use
and worth covering under our BBP.

Cargo.toml

@@ -34,6 +34,10 @@ members = [
   "crypto/schnorr",
   "crypto/dleq",
   "crypto/dkg",
+  "crypto/dkg/recovery",
+  "crypto/dkg/promote",
+  "crypto/dkg/musig",
+  "crypto/dkg/pedpop",
   "crypto/frost",
   "crypto/schnorrkel",