Mark all generated C# classes with [GeneratedCode] attribute #1086

Job	Run time
cpp-lib-build (macos-12, clang, ON)	1m 22s
build (macos-12, tool)	1m 32s
build (macos-12, cpp)	15m 20s
build (macos-12, csharp)	5m 5s
cpp-lib-build (macos-12, clang, OFF)	1m 29s
build (macos-12, dart)	3m 54s
cpp-lib-build (macos-12, gcc, ON)	2m 37s
build (macos-12, go)	3m 17s
cpp-lib-build (macos-12, gcc, OFF)	3m 4s
build (macos-12, java)	1m 45s
cpp-lib-build (ubuntu-20.04, clang, ON)	54s
build (macos-12, javascript)	2m 52s
cpp-lib-build (ubuntu-20.04, clang, OFF)	1m 22s
build (macos-12, typescript)	13m 32s
build (macos-12, php)	2m 50s
cpp-lib-build (ubuntu-20.04, gcc, ON)	1m 0s
build (macos-12, python3)	2m 0s
cpp-lib-build (ubuntu-20.04, gcc, OFF)	1m 8s
cpp-lib-build (windows-2022, clang, ON)	4m 49s
build (ubuntu-20.04, tool)	57s
cpp-lib-build (windows-2022, clang, OFF)	5m 48s
build (ubuntu-20.04, cpp)	14m 59s
cpp-lib-build (windows-2022, cl)	4m 44s
build (ubuntu-20.04, csharp)	4m 47s
build (ubuntu-20.04, dart)	3m 36s
build (ubuntu-20.04, go)	2m 22s
build (ubuntu-20.04, java)	1m 8s
build (ubuntu-20.04, javascript)	1m 37s
build (ubuntu-20.04, typescript)	9m 46s
build (ubuntu-20.04, php)	1m 47s
build (ubuntu-20.04, python3)	1m 4s
build (windows-2022, tool)	2m 5s
build (windows-2022, cpp)	22m 55s
build (windows-2022, csharp)	9m 23s
build (windows-2022, dart)	4m 16s
build (windows-2022, go)	6m 14s
build (windows-2022, java)	2m 4s
build (windows-2022, javascript)	2m 33s
build (windows-2022, typescript)	21m 13s
build (windows-2022, php)	2m 27s
build (windows-2022, python3)	1m 55s
	3h 17m 32s

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