Refactor/number formatting

[grisumbras]

[codecov[bot]]

Codecov Report

Merging #853 (b7b6382) into develop (22c1b39) will increase coverage by 0.00%. The diff coverage is 100.00%.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #853   +/-   ##
========================================
  Coverage    99.19%   99.19%           
========================================
  Files           70       70           
  Lines         6849     6859   +10     
========================================
+ Hits          6794     6804   +10     
  Misses          55       55           

Impacted Files	Coverage Δ
include/boost/json/detail/impl/format.ipp	100.00% <100.00%> (ø)
include/boost/json/detail/stream.hpp	100.00% <100.00%> (ø)
include/boost/json/impl/serializer.ipp	98.62% <100.00%> (ø)

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[cppalliance-bot]

Benchmark test results. More info at https://benchmark.cppalliance.org/jsonbenchmarks-pullrequests/853/pullrequest.html