airframe-http: Add HttpClient

[xerial]

Add a common interface and finagle-based implementation for an http client. #472

• Simplify Retryer (=> RetryContext) to support http error handling airframe-control: Remove context from Control.Retrier #467 Retryer -> RetryContext #491
• Add HttpStatus code representations using type classes (xxxAdapter)
• Add a standard HTTP response hander Add a basic retry pattern set for HTTP requests #366
• Add a finagle-based HTTP client
• Add async/sync http clients. Using F[_] as an abstraction of Future. This is useful to remove the dependency to Finagle in airframe-http.
• Support circuit breaker (No code for this. We can use circuit breaker of Finagle by customizing FinagleClientConfig.initClient)
• Integrate control.Retry and FinagleRetryFilter.
  • Finagle will not enable request retry by default, so we anyway need to add our own retry filter.
  • Simplified control.Retry so that we can use this retry logic both for imperative programming and Future-based programming.
• Support response/request -> object mapping with airframe-codec.

[codecov]

Codecov Report

Merging #482 into master will decrease coverage by 0.17%.
The diff coverage is 90.64%.

@@            Coverage Diff             @@
##           master     #482      +/-   ##
==========================================
- Coverage   83.79%   83.62%   -0.18%     
==========================================
  Files         193      200       +7     
  Lines        7586     7919     +333     
  Branches      684      699      +15     
==========================================
+ Hits         6357     6622     +265     
- Misses       1229     1297      +68

Impacted Files	Coverage Δ
...rc/main/scala/wvlet/airframe/http/HttpStatus.scala	100% <100%> (ø)
...rc/main/scala/wvlet/airframe/http/HttpClient.scala	100% <100%> (ø)
.../main/scala/wvlet/airframe/http/RouteMatcher.scala	92.53% <100%> (+0.11%)	⬆️
...ttp/src/main/scala/wvlet/airframe/http/Route.scala	100% <100%> (ø)	⬆️
...ain/scala/wvlet/airframe/control/ResultClass.scala	100% <100%> (ø)
...tp/src/main/scala/wvlet/airframe/http/Router.scala	100% <100%> (ø)	⬆️
.../scala/wvlet/airframe/http/HttpResponseCodec.scala	54.54% <54.54%> (ø)
...cala/wvlet/airframe/http/HttpClientException.scala	76.27% <76.27%> (ø)
...http/src/main/scala/wvlet/airframe/http/Http.scala	80% <80%> (-20%)	⬇️
...let/airframe/http/finagle/FinagleRetryFilter.scala	89.47% <89.47%> (ø)
... and 21 more

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[takezoe]

@xerial Thanks for your great work! I have some questions on it just to be sure. Please can you take a look?

[xerial]

CI is failing because of jdk11 download failure. Other than that, we are good to merge this PR.

[takezoe]

@xerial Thanks for your quick fix!