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ARROW-11100: [Rust] Speed up numeric to string cast using lexical_core

Uses lexical_core to speed up num to string casts.

This gets a nice speed up, especially for floats:
```
cast i64 to string 512  time:   [22.209 us 22.462 us 22.885 us]
                        change: [-38.438% -37.979% -37.154%] (p = 0.00 < 0.05)
                        Performance has improved.
Found 14 outliers among 100 measurements (14.00%)
  11 (11.00%) low mild
  3 (3.00%) high severe

Benchmarking cast f32 to string 512: Collecting 100 samples in estimated 5.0698                                                                                 cast f32 to string 512  time:   [25.587 us 25.692 us 25.786 us]
                        change: [-62.364% -62.215% -62.076%] (p = 0.00 < 0.05)
                        Performance has improved.
Found 7 outliers among 100 measurements (7.00%)
  1 (1.00%) low severe
  1 (1.00%) low mild
  4 (4.00%) high mild
  1 (1.00%) high severe
```

Closes #9068 from Dandandan/numeric_cast_lexical

Authored-by: Heres, Daniel <danielheres@gmail.com>
Signed-off-by: Jorge C. Leitao <jorgecarleitao@gmail.com>