Copy PL/pgSQL regression tests in Makefile #594

Job	Run time
build (ubuntu-20.04, clang, protobuf-c, valgrind)	3m 55s
build (ubuntu-20.04, clang, protobuf-c, no-valgrind)	1m 4s
build_windows_msvc (x64)	1m 3s
build_windows_msys2 (mingw64)	3m 24s
build_windows_msvc (x86)	1m 16s
build (ubuntu-20.04, clang, protobuf-cpp, valgrind)	33m 24s
build_windows_msys2 (mingw32)	3m 1s
build (ubuntu-20.04, clang, protobuf-cpp, no-valgrind)	4m 3s
build_windows_msys2 (ucrt64)	3m 21s
build (ubuntu-20.04, gcc, protobuf-c, valgrind)	3m 19s
build_windows_msys2 (clang64)	2m 13s
build (ubuntu-20.04, gcc, protobuf-c, no-valgrind)	55s
build (ubuntu-20.04, gcc, protobuf-cpp, valgrind)	33m 29s
build (ubuntu-20.04, gcc, protobuf-cpp, no-valgrind)	4m 16s
	1h 38m 43s

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