Expose the runtime-benchmarks feature to the cli crate (#5143)

This exposes the `runtime-benchmarks` feature via the cli crate and
makes sure the benchmarking can be enabled. This requires that the user
goes to `bin/node/cli` and runs `cargo build --features
runtime-benchmarks` to build a node that has the feature enabled.

substrate/bin/node/runtime/Cargo.toml

@@ -132,4 +132,9 @@ std = [
 	"pallet-recovery/std",
 	"pallet-vesting/std",
 ]
-runtime-benchmarks = ["frame-benchmarking"]
+runtime-benchmarks = [
+	"frame-benchmarking",
+	"pallet-timestamp/runtime-benchmarks",
+	"pallet-identity/runtime-benchmarks",
+	"pallet-balances/runtime-benchmarks",
+]