WIP: Add parley to benchmarks

[nicoburns]

Not sure if you'd want to merge this, but putting this up so that benchmark code is public.

Please do let me know if there are any issues with my benchmarking methodology.

Results

+---------------------------+-------------+-----------+
| Benchmark                 | Cosmic Text | Parley    |
+---------------------------+-------------+-----------+
| ShapeLine/ASCII Fast Path | 2.0745 ms   | 580.13 µs |
| ShapeLine/Mixed-Language  | 13.897 ms   | 3.9151 ms |
| ShapeLine/Layout Heavy    | 4.4262 ms   | 1.1573 ms |
| ShapeLine/Combined Stress | 22.514 ms   | 6.0847 ms |
+---------------------------+-------------+-----------+

[jackpot51]

I get the following results running cargo bench ShapeLine locally with this branch:

     Running benches/text_shaping_benchmarks.rs (target/release/deps/text_shaping_benchmarks-d8f9c47bd50fc487)
ShapeLine/ASCII Fast Path/cosmic_text
                        time:   [571.33 µs 573.06 µs 575.33 µs]
Found 1 outliers among 100 measurements (1.00%)
  1 (1.00%) high severe
ShapeLine/ASCII Fast Path/parley
                        time:   [673.96 µs 675.06 µs 676.27 µs]

Benchmarking ShapeLine/BiDi Processing/cosmic_text: Warming up for 3.0000 s
Warning: Unable to complete 100 samples in 5.0s. You may wish to increase target time to 5.4s, enable flat sampling, or reduce sample count to 60.
ShapeLine/BiDi Processing/cosmic_text
                        time:   [1.0733 ms 1.0761 ms 1.0792 ms]
Found 3 outliers among 100 measurements (3.00%)
  2 (2.00%) high mild
  1 (1.00%) high severe
Benchmarking ShapeLine/BiDi Processing/parley: Warming up for 3.0000 s
Warning: Unable to complete 100 samples in 5.0s. You may wish to increase target time to 6.6s, enable flat sampling, or reduce sample count to 60.
ShapeLine/BiDi Processing/parley
                        time:   [1.2937 ms 1.2965 ms 1.3001 ms]
Found 1 outliers among 100 measurements (1.00%)
  1 (1.00%) high mild

ShapeLine/Mixed-Language Text/cosmic_text
                        time:   [5.9126 ms 5.9566 ms 6.0044 ms]
Found 7 outliers among 100 measurements (7.00%)
  5 (5.00%) high mild
  2 (2.00%) high severe
ShapeLine/Mixed-Language Text/parley
                        time:   [8.9927 ms 9.0322 ms 9.0754 ms]
Found 5 outliers among 100 measurements (5.00%)
  4 (4.00%) high mild
  1 (1.00%) high severe

Benchmarking ShapeLine/Layout Heavy/cosmic_text: Warming up for 3.0000 s
Warning: Unable to complete 100 samples in 5.0s. You may wish to increase target time to 5.6s, enable flat sampling, or reduce sample count to 60.
ShapeLine/Layout Heavy/cosmic_text
                        time:   [1.1076 ms 1.1094 ms 1.1112 ms]
Found 14 outliers among 100 measurements (14.00%)
  5 (5.00%) low severe
  5 (5.00%) low mild
  4 (4.00%) high mild
Benchmarking ShapeLine/Layout Heavy/parley: Warming up for 3.0000 s
Warning: Unable to complete 100 samples in 5.0s. You may wish to increase target time to 6.4s, enable flat sampling, or reduce sample count to 60.
ShapeLine/Layout Heavy/parley
                        time:   [1.2850 ms 1.2867 ms 1.2885 ms]
Found 9 outliers among 100 measurements (9.00%)
  3 (3.00%) low mild
  2 (2.00%) high mild
  4 (4.00%) high severe

ShapeLine/Combined Stress/cosmic_text
                        time:   [6.3641 ms 6.3836 ms 6.4050 ms]
Found 7 outliers among 100 measurements (7.00%)
  6 (6.00%) high mild
  1 (1.00%) high severe
ShapeLine/Combined Stress/parley
                        time:   [8.1593 ms 8.1817 ms 8.2075 ms]
Found 7 outliers among 100 measurements (7.00%)
  5 (5.00%) high mild
  2 (2.00%) high severe