Improve Performance of JSON Unforming

[alexanderkiel]

Instead of literal unforming of the internal FHIR data structures to a format usable by most JSON serializers like Cheshire, I just implement the JSONable of Cheshire directly at the primitive types. So I don't have to rebuild the maps representing non-primitive types to the extend previously.

[codecov]

Codecov Report

Merging #308 (fee20f4) into develop (1544f67) will increase coverage by 0.30%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop     #308      +/-   ##
===========================================
+ Coverage    87.47%   87.78%   +0.30%     
===========================================
  Files          196      196              
  Lines        12062    12106      +44     
  Branches       482      483       +1     
===========================================
+ Hits         10551    10627      +76     
+ Misses        1029      996      -33     
- Partials       482      483       +1     

Impacted Files	Coverage Δ
...r-structure/src/blaze/fhir/spec/type/protocols.clj	100.00% <ø> (ø)
...odules/fhir-structure/src/blaze/fhir/spec/impl.clj	93.95% <100.00%> (ø)
...odules/fhir-structure/src/blaze/fhir/spec/type.clj	87.60% <100.00%> (+7.05%)	⬆️
...dules/interaction/src/blaze/interaction/update.clj	95.52% <0.00%> (-1.50%)	⬇️