A more performant implementation of [fmt::Display] (and [fmt::Debug])
for the standard library's [Ipv4Addr] struct.
Rough benchmarks (using Rust 1.59.0) show almost 3x improvements:
```bash $ cargo version cargo 1.59.0 (49d8809dc 2022-02-10) $ cargo bench std 23.24.25.26 time: [101.75 ns 105.13 ns 108.69 ns] Found 3 outliers among 100 measurements (3.00%) 2 (2.00%) high mild 1 (1.00%) high severe
ipv4-display 23.24.25.26 time: [35.706 ns 36.657 ns 37.710 ns] Found 3 outliers among 100 measurements (3.00%) 3 (3.00%) high mild
std 213.2.33.213 time: [111.03 ns 113.84 ns 116.89 ns] Found 4 outliers among 100 measurements (4.00%) 4 (4.00%) high mild
ipv4-display 213.2.33.213 time: [36.145 ns 37.188 ns 38.307 ns] Found 2 outliers among 100 measurements (2.00%) 2 (2.00%) high mild ```