Refactor pgp_encrypted_material_t to C++ classes. #2028

Job	Run time
windows-latest msys2 [msystem ucrt64; backend botan; build shared libs on; GnuPG stable]	8m 48s
windows-latest msys2 [msystem ucrt64; backend botan; build shared libs on; GnuPG stable]	8m 48s
windows-latest msys2 [msystem ucrt64; backend openssl; build shared libs on; GnuPG stable]	7m 4s
windows-latest msys2 [msystem ucrt64; backend openssl; build shared libs on; GnuPG stable]	7m 13s
windows-latest msys2 [msystem mingw64; backend botan; build shared libs on; GnuPG stable]	8m 8s
windows-latest msys2 [msystem mingw64; backend botan; build shared libs on; GnuPG stable]	8m 8s
windows-latest msys2 [msystem mingw64; backend openssl; build shared libs on; GnuPG stable]	7m 22s
windows-latest msys2 [msystem mingw64; backend openssl; build shared libs on; GnuPG stable]	7m 22s
windows-latest msys2 [msystem clang64; backend botan; build shared libs on; GnuPG stable]	8m 0s
windows-latest msys2 [msystem clang64; backend botan; build shared libs on; GnuPG stable]	8m 0s
windows-latest msys2 [msystem clang64; backend openssl; build shared libs on; GnuPG stable]	6m 49s
windows-latest msys2 [msystem clang64; backend openssl; build shared libs on; GnuPG stable]	6m 49s
windows-latest msys2 [msystem ucrt64; backend botan; build shared libs off; GnuPG stable]	8m 23s
windows-latest msys2 [msystem ucrt64; backend botan; build shared libs off; GnuPG stable]	8m 23s
	1h 49m 17s

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