Refactor/codableutils

[prafsoni]

• [refactor] EncodableUtils new common protocol ValueWrapper for CodableValue, DecodableValue and EncodableValue, rename NullValue to NilValue, removed protocols EncodableWrapper, DecodableWrapper and CodableWrapper
• [chore] add swift-log to unit tests
• [fix] typo in logger label in ElasticClient

[codecov[bot]]

Codecov Report

Merging #56 into master will increase coverage by 1.89%. The diff coverage is 66.32%.

@@            Coverage Diff            @@
##           master     #56      +/-   ##
=========================================
+ Coverage      32%   33.9%   +1.89%     
=========================================
  Files          48      48              
  Lines        5152    5159       +7     
=========================================
+ Hits         1649    1749     +100     
+ Misses       3503    3410      -93

Impacted Files	Coverage Δ
Sources/ElasticSwift/ElasticSwift.swift	51.42% <ø> (ø)	:arrow_up:
...icSwiftCodableUtils/ElasticSwiftCodableUtils.swift	44.91% <66.32%> (+25.97%)	:arrow_up:
Sources/ElasticSwiftCore/Errors/CoreErrors.swift	42.85% <0%> (-21.43%)	:arrow_down:

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