Snowbridge Rococo deployment updates (#2792)

- Includes the introduction of the `fast-runtime` feature, which cleans
up our features
- Updates beacon client fork versions config to Sepolia's versions
- Cleanup of AgentIdOf

---------

Co-authored-by: Ron <yrong1997@gmail.com>
Co-authored-by: claravanstaden <Cats 4 life!>

cumulus/parachains/runtimes/bridge-hubs/bridge-hub-rococo/Cargo.toml

@@ -130,7 +130,7 @@ bridge-runtime-common = { path = "../../../../../bridges/bin/runtime-common", fe
 sp-keyring = { path = "../../../../../substrate/primitives/keyring" }
 
 [features]
-default = ["beacon-spec-mainnet", "std"]
+default = ["std"]
 std = [
 	"bp-asset-hub-rococo/std",
 	"bp-asset-hub-westend/std",
@@ -223,7 +223,6 @@ std = [
 ]
 
 runtime-benchmarks = [
-	"beacon-spec-mainnet",
 	"bridge-hub-common/runtime-benchmarks",
 	"bridge-runtime-common/runtime-benchmarks",
 	"cumulus-pallet-parachain-system/runtime-benchmarks",
@@ -299,8 +298,8 @@ try-runtime = [
 ]
 
 experimental = ["pallet-aura/experimental"]
-beacon-spec-mainnet = [
-	"snowbridge-ethereum-beacon-client/beacon-spec-mainnet",
+fast-runtime = [
+	"snowbridge-ethereum-beacon-client/beacon-spec-minimal",
 ]
 
 # A feature that should be enabled when the runtime should be built for on-chain