Allow bridge relayers to be built from repo (#3069)

* Bump Rococo/Wococo `spec_version` used by the bridge relayer

* Prevent bridge relayer from being part of workspace

This allows us to build the relayer without pulling in all its
dependencies into the Polkadot repo by indicating its manifest path when
building.

* Revert "Bump Rococo/Wococo `spec_version` used by the bridge relayer"

This reverts commit 90fdeecb.

Cargo.toml

@@ -80,6 +80,10 @@ members = [
 	"parachain/test-parachains/adder/collator",
 ]
 
+# We want to be able to build the bridge relayer without pulling it (and all of its
+# dependencies into the Polkadot workspace)
+exclude = ["bridges/relays/bin-substrate", "bridges/bin/rialto/runtime", "bridges/bin/millau/runtime"]
+
 [badges]
 maintenance = { status = "actively-developed" }