Allow to skip middlewares stack for simple field resolvers

[MichalLytek]

Closes #254 and #449

[codecov]

Codecov Report

Merging #479 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #479      +/-   ##
==========================================
+ Coverage   95.12%   95.14%   +0.01%     
==========================================
  Files          75       75              
  Lines        1314     1318       +4     
  Branches      249      252       +3     
==========================================
+ Hits         1250     1254       +4     
  Misses         61       61              
  Partials        3        3

Impacted Files	Coverage Δ
src/decorators/Field.ts	100% <ø> (ø)	⬆️
src/decorators/ObjectType.ts	100% <ø> (ø)	⬆️
src/decorators/Arg.ts	100% <ø> (ø)	⬆️
src/decorators/InterfaceType.ts	100% <ø> (ø)	⬆️
src/decorators/Resolver.ts	100% <ø> (ø)	⬆️
src/resolvers/create.ts	100% <100%> (ø)	⬆️
src/schema/schema-generator.ts	96.74% <100%> (+0.05%)	⬆️
src/decorators/index.ts	100% <100%> (ø)	⬆️

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