Add a parse-self benchmark for `.debug_info` and `EndianRcSlice
Add a parse-self benchmark for `.debug_info` and `EndianRcSlice

Looks like it takes about 1.58x the time that using `EndianSlice` does:

```
test bench_parsing_debug_info                                  ... bench:   2,261,953 ns/iter (+/- 142,827)
test bench_parsing_debug_info_with_endian_rc_slice             ... bench:   3,564,292 ns/iter (+/- 208,038)
```

gimli-rs/gimli,gimli-rs/gimli