CsCompleter: Implement GoToDocumentOutline. #607

Job	Run time
C++ Lint	5m 51s
ubuntu-20.04 - C++ Benchmark	1m 45s
ubuntu-20.04 - test run	19m 1s
Windows MSVC 17 x64 - C++ Benchmark	4m 15s
macos-12 - C++ Benchmark	2m 4s
Windows MSVC 17 x64 - test run	28m 53s
macos-12 - test run	23m 58s
Windows MSVC 17 x86 - test run	29m 21s
ubuntu-20.04 - with Clang compiler - test run	19m 0s
Windows MSVC 16 x64 - test run	29m 20s
ubuntu-20.04 - without libclang completer - test run	18m 23s
	3h 1m 51s

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