test: Display benchmark results with thousands separators

test: Display benchmark results with thousands separators

Example display:

```
running 9 tests
test a ... bench:           0 ns/iter (+/- 0)
test b ... bench:          52 ns/iter (+/- 0)
test c ... bench:          88 ns/iter (+/- 0)
test d ... bench:         618 ns/iter (+/- 111)
test e ... bench:       5,933 ns/iter (+/- 87)
test f ... bench:      59,280 ns/iter (+/- 1,052)
test g ... bench:     588,672 ns/iter (+/- 3,381)
test h ... bench:   5,894,227 ns/iter (+/- 303,489)
test i ... bench:  59,112,382 ns/iter (+/- 1,500,110)
```

Fixes #10953
Fixes #26109