[RFC] Switch C# completer to LSP #747

Job	Run time
C++ Lint	6m 10s
Windows MSVC 17 x64 - C++ Benchmark	4m 13s
ubuntu-24.04 - C++ Benchmark	2m 10s
Windows MSVC 17 x64 - test run	42m 54s
ubuntu-24.04 - test run	26m 44s
Windows MSVC 17 x86 - test run	58m 52s
macos-14 - C++ Benchmark	1m 46s
Windows MSVC 16 x64 - test run	41m 2s
macos-14 - test run	20m 43s
ubuntu-24.04 - with Clang compiler - test run	24m 21s
ubuntu-24.04 - without libclang completer - test run	25m 33s
	4h 14m 28s

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