Use os.signpost and os.log for better logging and profiling

[toshi0383]

Now we can visualize network requests in instruments' "os_signpost" trace.
Network request/response performance is automatically logged via os_signpost.

• Fix Bugs Faster using Activity Tracing: WWDC 2014
• Unified Logging and Activity Tracing: WWDC 2016
• Measuring Performance Using Logging: WWDC 2018

[codecov-io]

Codecov Report

Merging #50 into master will increase coverage by <.01%.
The diff coverage is 0%.

@@            Coverage Diff            @@
##           master     #50      +/-   ##
=========================================
+ Coverage    4.96%   4.96%   +<.01%     
=========================================
  Files          40      40              
  Lines        1692    1691       -1     
=========================================
  Hits           84      84              
+ Misses       1608    1607       -1

Impacted Files	Coverage Δ
...Sources/List/Builds/BuildsListViewController.swift	0% <ø> (ø)	⬆️
...ent/Sources/List/Builds/BuildsPollingManager.swift	0% <0%> (ø)	⬆️
...ient/Sources/List/Builds/BuildsListViewModel.swift	0% <0%> (ø)	⬆️
BitriseClient/Sources/Extension/APIKit+Rx.swift	0% <0%> (ø)	⬆️
...lient/Sources/BitriseYml/BitriseYmlViewModel.swift	0% <0%> (ø)	⬆️

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