*: add lru cache to speed up scanning logs

[BusyJay]

# Master:
test engine::tests::bench_engine_fetch_entries              ... bench:      23,738 ns/iter (+/- 1,027)

# This PR:
test engine::tests::bench_engine_fetch_entries              ... bench:      18,127 ns/iter (+/- 517)

It's not a fair comparison because thread local cache can only cache a block, but global lru cache can cache 256MiB. But it's just a way to show potential improvement on scanning logs.

[codecov]

Codecov Report

Patch coverage: 94.21% and project coverage change: -0.07 ⚠️

Comparison is base (39f4db4) 97.89% compared to head (02f4c85) 97.82%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #302      +/-   ##
==========================================
- Coverage   97.89%   97.82%   -0.07%     
==========================================
  Files          31       32       +1     
  Lines       12228    12435     +207     
==========================================
+ Hits        11970    12164     +194     
- Misses        258      271      +13     

Impacted Files	Coverage Δ
src/lib.rs	100.00% <ø> (ø)
src/cache.rs	93.51% <93.51%> (ø)
src/engine.rs	98.54% <95.08%> (-0.10%)	⬇️
src/config.rs	98.09% <100.00%> (+<0.01%)	⬆️
src/filter.rs	82.39% <100.00%> (-0.07%)	⬇️
src/log_batch.rs	98.07% <100.00%> (+<0.01%)	⬆️
src/pipe_log.rs	95.45% <100.00%> (ø)
src/purge.rs	97.46% <100.00%> (+0.01%)	⬆️

... and 2 files with indirect coverage changes

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