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/cli/Cargo.toml

@@ -151,3 +151,4 @@ wasmtime = [
 	"sc-cli/wasmtime",
 	"sc-service/wasmtime",
 ]
+runtime-benchmarks = [ "node-runtime/runtime-benchmarks" ]