Calculate token usage in parallel via Rayon

What?
=====

This swaps token usage calculation with Rayon to further speed up
processing.

|            | before | after | speedup |
| Codebase 1 |    778 |   621 |     25% |
| Codebase 2 |   1214 |   985 |     23% |
| Codebase 3 |  37980 | 36950 |      3% |
|  discourse |   1309 |   949 |     38% |

All times are measured in milliseconds and benchmarks are run with
[bench](https://hackage.haskell.org/package/bench) against release mode.

crates/token_analysis/Cargo.toml

@@ -13,7 +13,8 @@ project_configuration = { path = "../../crates/project_configuration/" }
 serde_json = "1.0.50"
 serde = { version = "1.0.105", features = ["derive"] }
 itertools = "0.9"
-indicatif = {version = "0.14"}
+rayon = "1.1"
+indicatif = {version = "0.14", features = ["with_rayon"]}
 
 [dev-dependencies]
 totems = "0.2.7"

crates/token_analysis/src/token_usage.rs

@@ -1,9 +1,10 @@
 use super::analysis_filter::{AnalysisFilter, OrderField, SortOrder};
 use super::occurrence_count::FileTypeCounts;
 use super::usage_likelihood::UsageLikelihood;
-use indicatif::ProgressIterator;
+use indicatif::ParallelProgressIterator;
 use itertools::{rev, Itertools};
 use project_configuration::ProjectConfiguration;
+use rayon::prelude::*;
 use serde::Serialize;
 use token_search::{TokenSearchConfig, TokenSearchResult, TokenSearchResults};
 
@@ -46,9 +47,9 @@ impl TokenUsageResults {
         let size = &unwrapped_results.len();
 
         let results = unwrapped_results
-            .into_iter()
+            .par_iter()
             .progress_with(token_search_config.toggleable_progress_bar("🧐 Analyzing...", *size))
-            .map(|r| TokenUsage::new(config, r))
+            .map(|r| TokenUsage::new(config, r.clone()))
             .collect::<Vec<_>>();
         TokenUsageResults(results)
     }