Add IFileSystemHandler to support Azure for StaticMapping location

[StefH]

No description provided.

[codecov]

Codecov Report

Merging #180 into master will increase coverage by 1.03%.
The diff coverage is 61.7%.

@@            Coverage Diff             @@
##           master     #180      +/-   ##
==========================================
+ Coverage   70.15%   71.19%   +1.03%     
==========================================
  Files          88       89       +1     
  Lines        3207     3236      +29     
  Branches      423      425       +2     
==========================================
+ Hits         2250     2304      +54     
+ Misses        783      763      -20     
+ Partials      174      169       -5

Impacted Files	Coverage Δ
src/WireMock.Net/Server/FluentMockServer.cs	52.38% <ø> (ø)	⬆️
.../WireMock.Net/Settings/FluentMockServerSettings.cs	100% <100%> (ø)	⬆️
src/WireMock.Net/Util/FileHelper.cs	100% <100%> (+58.33%)	⬆️
...rc/WireMock.Net/Handlers/LocalFileSystemHandler.cs	52.63% <52.63%> (ø)
src/WireMock.Net/Server/FluentMockServer.Admin.cs	47.16% <62.5%> (+4.14%)	⬆️
src/WireMock.Net/Serialization/MappingConverter.cs	25.86% <0%> (+0.86%)	⬆️
src/WireMock.Net/Serialization/MatcherMapper.cs	77.77% <0%> (+17.77%)	⬆️

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