Add: Conversion ops for custom Optional class #504

Job	Run time
build_windows_deprecated_extensions	4m 20s
build_windows (NO)	3m 41s
build_linux (gcc-9, ubuntu-22.04, NO)	3m 2s
build_windows (YES)	4m 3s
build_linux_deprecated_extensions (gcc-9, ubuntu-22.04)	2m 28s
build_linux (gcc-10, ubuntu-22.04, NO)	2m 30s
build_linux_deprecated_extensions (gcc-10, ubuntu-22.04)	2m 23s
build_linux_deprecated_extensions (clang-13, ubuntu-22.04)	2m 36s
build_linux (gcc-10, ubuntu-22.04, YES)	2m 41s
build_linux_deprecated_extensions (ubuntu-24.04, gcc-14, g++-14)	2m 31s
build_linux_deprecated_extensions (ubuntu-24.04, clang-18, clang++-18)	2m 48s
build_linux (clang-13, ubuntu-22.04, NO)	2m 44s
build_linux (clang-15, ubuntu-22.04, NO)	2m 44s
build_linux (clang-15, ubuntu-22.04, YES)	2m 45s
build_linux (ubuntu-24.04, gcc-14, g++-14)	2m 34s
build_linux (ubuntu-24.04, clang-18, clang++-18)	2m 39s
	46m 29s

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