Add support for DocumentSymbol in document outline requests #773

Job	Run time
C++ Lint	11m 12s
Windows MSVC 17 x64 - C++ Benchmark	4m 19s
ubuntu-24.04 - C++ Benchmark	2m 3s
Windows MSVC 17 x64 - test run	35m 10s
ubuntu-24.04 - test run	29m 2s
Windows MSVC 17 x86 - test run	34m 35s
macos-14 - C++ Benchmark	1m 55s
macos-14 - test run	30m 19s
Windows MSVC 16 x64 - test run	39m 0s
ubuntu-24.04 - with Clang compiler - test run	26m 52s
ubuntu-24.04 - without libclang completer - test run	29m 4s
	4h 3m 31s

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