Refactor pgp_encrypted_material_t to C++ classes. #1099

Job	Run time
Windows-2022 [arch x64, toolset v143, backend botan, build shared libs off, use CMake prefix path on, sanitizers off]	15m 46s
Windows-2022 [arch x64, toolset v143, backend botan, build shared libs off, use CMake prefix path off, sanitizers off]	17m 28s
Windows-2022 [arch x64, toolset v143, backend openssl, build shared libs off, use CMake prefix path on, sanitizers off]	13m 34s
Windows-2022 [arch x64, toolset v143, backend openssl, build shared libs off, use CMake prefix path off, sanitizers off]	15m 37s
Windows-2022 [arch x64, toolset ClangCL, backend botan, build shared libs off, use CMake prefix path on, sanitizers off]	15m 32s
Windows-2022 [arch x64, toolset ClangCL, backend botan, build shared libs off, use CMake prefix path off, sanitizers off]	17m 57s
Windows-2022 [arch x64, toolset ClangCL, backend openssl, build shared libs off, use CMake prefix path on, sanitizers off]	12m 19s
Windows-2022 [arch x64, toolset ClangCL, backend openssl, build shared libs off, use CMake prefix path off, sanitizers off]	15m 9s
Windows-2022 [arch x64, toolset v143, backend botan, build shared libs off, use CMake prefix path off, sanitizers on]	54m 33s
Windows-2022 [arch Win32, toolset ClangCL, backend botan, build shared libs off, use CMake prefix path on, sanitizers off]	20m 17s
Windows-2022 [arch Win32, toolset v143, backend openssl, build shared libs off, use CMake prefix path off, sanitizers off]	18m 9s
	3h 36m 21s

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