Refactor encrypted_add_password(). #1107

Job	Run time
Windows-2022 [arch x64, toolset v143, backend botan, build shared libs off, use CMake prefix path on, sanitizers off]	15m 39s
Windows-2022 [arch x64, toolset v143, backend botan, build shared libs off, use CMake prefix path off, sanitizers off]	16m 42s
Windows-2022 [arch x64, toolset v143, backend openssl, build shared libs off, use CMake prefix path on, sanitizers off]	18m 6s
Windows-2022 [arch x64, toolset v143, backend openssl, build shared libs off, use CMake prefix path off, sanitizers off]	11m 18s
Windows-2022 [arch x64, toolset ClangCL, backend botan, build shared libs off, use CMake prefix path on, sanitizers off]	17m 20s
Windows-2022 [arch x64, toolset ClangCL, backend botan, build shared libs off, use CMake prefix path off, sanitizers off]	16m 52s
Windows-2022 [arch x64, toolset ClangCL, backend openssl, build shared libs off, use CMake prefix path on, sanitizers off]	16m 43s
Windows-2022 [arch x64, toolset ClangCL, backend openssl, build shared libs off, use CMake prefix path off, sanitizers off]	14m 57s
Windows-2022 [arch x64, toolset v143, backend botan, build shared libs off, use CMake prefix path off, sanitizers on]	26m 58s
Windows-2022 [arch Win32, toolset ClangCL, backend botan, build shared libs off, use CMake prefix path on, sanitizers off]	17m 56s
Windows-2022 [arch Win32, toolset v143, backend openssl, build shared libs off, use CMake prefix path off, sanitizers off]	15m 56s
	3h 8m 27s

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