[subsystem-benchmarks] Save results to json (#3829)

Here we add the ability to save subsystem benchmark results in JSON
format to display them as graphs

To draw graphs, CI team will use
[github-action-benchmark](https://github.com/benchmark-action/github-action-benchmark).
Since we are using custom benchmarks, we need to prepare [a specific
data
type](https://github.com/benchmark-action/github-action-benchmark?tab=readme-ov-file#examples):
```
[
    {
        "name": "CPU Load",
        "unit": "Percent",
        "value": 50
    }
]
```

Then we'll get graphs like this: 

![example](https://raw.githubusercontent.com/rhysd/ss/master/github-action-benchmark/main.png)

[A live page with
graphs](https://benchmark-action.github.io/github-action-benchmark/dev/bench/)

---------

Co-authored-by: ordian <write@reusable.software>

polkadot/node/subsystem-bench/src/lib/environment.rs

@@ -404,7 +404,7 @@ impl TestEnvironment {
 		let total_cpu = test_env_cpu_metrics.sum_by("substrate_tasks_polling_duration_sum");
 
 		usage.push(ResourceUsage {
-			resource_name: "Test environment".to_string(),
+			resource_name: "test-environment".to_string(),
 			total: total_cpu,
 			per_block: total_cpu / num_blocks,
 		});