Add override specifier to typescript copyfrom codegen #1003

Job	Run time
build (macos-11, tool)	1m 53s
build (macos-11, cpp)	32m 49s
cpp-lib-build (macos-11, clang, ON)	9m 15s
build (macos-11, csharp)	11m 13s
cpp-lib-build (macos-11, clang, OFF)	9m 31s
build (macos-11, dart)	5m 46s
build (macos-11, go)	4m 42s
cpp-lib-build (macos-11, gcc, ON)	8m 2s
cpp-lib-build (macos-11, gcc, OFF)	8m 11s
build (macos-11, java)	2m 4s
cpp-lib-build (ubuntu-20.04, clang, ON)	3m 22s
build (macos-11, javascript)	2m 35s
cpp-lib-build (ubuntu-20.04, clang, OFF)	3m 16s
build (macos-11, typescript)	17m 59s
cpp-lib-build (ubuntu-20.04, gcc, ON)	4m 31s
build (macos-11, php)	21s
cpp-lib-build (ubuntu-20.04, gcc, OFF)	4m 50s
build (macos-11, python3)	2m 9s
cpp-lib-build (windows-2022, clang, ON)	4m 27s
build (ubuntu-20.04, tool)	55s
cpp-lib-build (windows-2022, clang, OFF)	5m 27s
build (ubuntu-20.04, cpp)	17m 33s
cpp-lib-build (windows-2022, cl)	4m 28s
build (ubuntu-20.04, csharp)	4m 42s
build (ubuntu-20.04, dart)	3m 37s
build (ubuntu-20.04, go)	2m 21s
build (ubuntu-20.04, java)	1m 12s
build (ubuntu-20.04, javascript)	1m 20s
build (ubuntu-20.04, typescript)	9m 53s
build (ubuntu-20.04, php)	1m 20s
build (ubuntu-20.04, python3)	1m 7s
build (windows-2022, tool)	1m 42s
build (windows-2022, cpp)	21m 45s
build (windows-2022, csharp)	7m 49s
build (windows-2022, dart)	4m 32s
build (windows-2022, go)	5m 33s
build (windows-2022, java)	1m 46s
build (windows-2022, javascript)	2m 8s
build (windows-2022, typescript)	21m 4s
build (windows-2022, php)	2m 7s
build (windows-2022, python3)	1m 38s
	4h 20m 55s

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