Make reinitialize_command's return type Generic when "command" argument is a Command #1189

Job	Run time
test_cygwin (39, windows-latest)	3m 11s
ci_setuptools (3.10, ubuntu-latest)	11s
test (3.8, ubuntu-latest)	23s
collateral (diffcov)	27s
test (3.8, macos-latest)	24s
test_msvc_python_mingw	1m 29s
collateral (docs)	28s
test (3.8, windows-latest)	23s
test_msys2_mingw (mingw64, x86_64, gcc, g++)	1m 24s
test (3.13, ubuntu-latest)	36s
test_msys2_mingw (mingw32, i686, gcc, g++)	1m 24s
test (3.13, macos-latest)	33s
test_msys2_mingw (ucrt64, ucrt-x86_64, gcc, g++)	1m 28s
test (3.13, windows-latest)	24s
test_msys2_mingw (clang64, clang-x86_64, clang, clang++)	1m 32s
test (3.9, ubuntu-latest)	28s
test (3.10, ubuntu-latest)	27s
test (3.11, ubuntu-latest)	22s
test (3.12, ubuntu-latest)	29s
test (3.14, ubuntu-latest)	36s
test (pypy3.10, ubuntu-latest)	37s
check	1s
release	0s
	17m 17s

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