chin and chmatch length 1 speedup

[mattdowle]

Implemented Michael's suggestion here: #4117 (comment)

[MichaelChirico]

Great! Let's sort the table in is_utc by frequency then (UTC>GMT>Etc/UTC>...). Here, or a separate PR?

[mattdowle]

Ok. In this PR might as well. I'll wait for your commit before merging.

[codecov]

Codecov Report

Merging #4121 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master   #4121      +/-   ##
=========================================
+ Coverage    99.4%   99.4%   +<.01%     
=========================================
  Files          72      72              
  Lines       13686   13695       +9     
=========================================
+ Hits        13605   13614       +9     
  Misses         81      81

Impacted Files	Coverage Δ
src/chmatch.c	100% <100%> (ø)	⬆️
R/utils.R	100% <100%> (ø)	⬆️

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