[subsystem-benchmarks] Add statement-distribution benchmarks (#3863)

Fixes https://github.com/paritytech/polkadot-sdk/issues/3748

Adds a subsystem benchmark for statements-distribution subsystem.

Results in CI (reference hw):
```
$ cargo bench -p polkadot-statement-distribution --bench statement-distribution-regression-bench --features subsystem-benchmarks

[Sent to peers] standart_deviation 0.07%
[Received from peers] standart_deviation 0.00%
[statement-distribution] standart_deviation 0.97%
[test-environment] standart_deviation 1.03%

Network usage, KiB                     total   per block
Received from peers                1088.0000    108.8000
Sent to peers                      1238.1800    123.8180

CPU usage, seconds                     total   per block
statement-distribution                0.3897      0.0390
test-environment                      0.4715      0.0472
```