Optimize Validate.fromPartial

[fthomas]

Benchmark results for this change:

master:
[info] Result "eu.timepit.refined.benchmark.RefineVBenchmark.refineV_Regex":
[info]   121.400 ±(99.9%) 1.297 ns/op [Average]
[info]   (min, avg, max) = (110.969, 121.400, 159.030), stdev = 5.493
[info]   CI (99.9%): [120.103, 122.698] (assumes normal distribution)
[info] # Run complete. Total time: 00:06:43
[info] Benchmark                       Mode  Cnt    Score   Error  Units
[info] RefineVBenchmark.refineV_Regex  avgt  200  121.400 ± 1.297  ns/op

this branch:
[info] Result "eu.timepit.refined.benchmark.RefineVBenchmark.refineV_Regex":
[info]   108.263 ±(99.9%) 0.893 ns/op [Average]
[info]   (min, avg, max) = (100.935, 108.263, 138.393), stdev = 3.780
[info]   CI (99.9%): [107.370, 109.156] (assumes normal distribution)
[info] # Run complete. Total time: 00:06:43
[info] Benchmark                       Mode  Cnt    Score   Error  Units
[info] RefineVBenchmark.refineV_Regex  avgt  200  108.263 ± 0.893  ns/op

[codecov]

Codecov Report

Merging #336 into master will decrease coverage by 2.56%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #336      +/-   ##
==========================================
- Coverage    99.1%   96.53%   -2.57%     
==========================================
  Files          38       38              
  Lines         447      462      +15     
  Branches        8        9       +1     
==========================================
+ Hits          443      446       +3     
- Misses          4       16      +12

Impacted Files	Coverage Δ
...c/main/scala/eu/timepit/refined/api/Validate.scala	100% <100%> (ø)	⬆️

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