subsystem-bench: Prepare CI output (#3158)

1. Benchmark results are collected in a single struct.
2. The output of the results is prettified.
3. The result struct used to save the output as a yaml and store it in
artifacts in a CI job.

```
$ cargo run -p polkadot-subsystem-bench --release -- test-sequence --path polkadot/node/subsystem-bench/examples/availability_read.yaml | tee output.txt
$ cat output.txt

polkadot/node/subsystem-bench/examples/availability_read.yaml #1

Network usage, KiB                     total   per block
Received from peers               510796.000  170265.333
Sent to peers                        221.000      73.667

CPU usage, s                           total   per block
availability-recovery                 38.671      12.890
Test environment                       0.255       0.085


polkadot/node/subsystem-bench/examples/availability_read.yaml #2

Network usage, KiB                     total   per block
Received from peers               413633.000  137877.667
Sent to peers                        353.000     117.667

CPU usage, s                           total   per block
availability-recovery                 52.630      17.543
Test environment                       0.271       0.090


polkadot/node/subsystem-bench/examples/availability_read.yaml #3

Network usage, KiB                     total   per block
Received from peers               424379.000  141459.667
Sent to peers                        703.000     234.333

CPU usage, s                           total   per block
availability-recovery                 51.128      17.043
Test environment                       0.502       0.167

```

```
$ cargo run -p polkadot-subsystem-bench --release -- --ci test-sequence --path polkadot/node/subsystem-bench/examples/availability_read.yaml | tee output.txt
$ cat output.txt
- benchmark_name: 'polkadot/node/subsystem-bench/examples/availability_read.yaml #1'
  network:
  - resource: Received from peers
    total: 509011.0
    per_block: 169670.33333333334
  - resource: Sent to peers
    total: 220.0
    per_block: 73.33333333333333
  cpu:
  - resource: availability-recovery
    total: 31.845848445
    per_block: 10.615282815
  - resource: Test environment
    total: 0.23582828799999941
    per_block: 0.07860942933333313

- benchmark_name: 'polkadot/node/subsystem-bench/examples/availability_read.yaml #2'
  network:
  - resource: Received from peers
    total: 411738.0
    per_block: 137246.0
  - resource: Sent to peers
    total: 351.0
    per_block: 117.0
  cpu:
  - resource: availability-recovery
    total: 18.93596025099999
    per_block: 6.31198675033333
  - resource: Test environment
    total: 0.2541994199999979
    per_block: 0.0847331399999993

- benchmark_name: 'polkadot/node/subsystem-bench/examples/availability_read.yaml #3'
  network:
  - resource: Received from peers
    total: 424548.0
    per_block: 141516.0
  - resource: Sent to peers
    total: 703.0
    per_block: 234.33333333333334
  cpu:
  - resource: availability-recovery
    total: 16.54178526900001
    per_block: 5.513928423000003
  - resource: Test environment
    total: 0.43960946299999537
    per_block: 0.14653648766666513
```

---------

Co-authored-by: Andrei Sandu <[email protected]>