Optimize grep search performance

[liuchengxu]

The key change is to avoid the unnecessary function call in the busy loop. Hyperfine indicates the performance is increased by 20+%.

hyperfine './maple-master grep --ripgrep --cmd-dir /home/xlc/Data2/github.com/paritytech/polkadot-sdk/ client' './maple grep --lib-ripgrep --cmd-dir /home/xlc/Data2/github.com/paritytech/polkadot-sdk/ client'
Benchmark 1: ./maple-master grep --ripgrep --cmd-dir /home/xlc/Data2/github.com/paritytech/polkadot-sdk/ client
  Time (mean ± σ):     640.4 ms ±  23.7 ms    [User: 1226.0 ms, System: 448.3 ms]
  Range (min … max):   579.1 ms … 664.8 ms    10 runs
 
Benchmark 2: ./maple grep --lib-ripgrep --cmd-dir /home/xlc/Data2/github.com/paritytech/polkadot-sdk/ client
  Time (mean ± σ):     514.5 ms ±  19.7 ms    [User: 1002.1 ms, System: 355.3 ms]
  Range (min … max):   467.0 ms … 531.7 ms    10 runs
 
Summary
  ./maple grep --lib-ripgrep --cmd-dir /home/xlc/Data2/github.com/paritytech/polkadot-sdk/ client ran
    1.24 ± 0.07 times faster than ./maple-master grep --ripgrep --cmd-dir /home/xlc/Data2/github.com/paritytech/polkadot-sdk/ client