Optimize `DoCrawl`
Benchmark:
```
cmake -S. -Bbuild-reld -G Ninja -DCMAKE_BUILD_TYPE=RelWithDebInfo -DBUILD_TESTING=ON
cmake --build build-reld --target crawl_benchmark && build-reld/crawl_benchmark
```
Before:
```
------------------------------------------------------
Benchmark Time CPU Iterations
------------------------------------------------------
BM_Crawl/1 3.53 ns 3.53 ns 198384032
BM_Crawl/4 54.3 ns 54.2 ns 12907171
BM_Crawl/16 733 ns 732 ns 955101
BM_Crawl/20 1142 ns 1141 ns 613766
```
After:
```
------------------------------------------------------
Benchmark Time CPU Iterations
------------------------------------------------------
BM_Crawl/1 1.36 ns 1.36 ns 453018506
BM_Crawl/4 5.59 ns 5.59 ns 124244505
BM_Crawl/16 102 ns 101 ns 6577269
BM_Crawl/20 147 ns 147 ns 4684004
```
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