Fuzz

Make `uint128` public since we return in a few places to the user #686

Job	Run time
posix (clang, clang++-12, 14,17,20, ubuntu-22.04, clang-12)	7m 52s
posix (clang, clang++-13, 14,17,20, ubuntu-22.04, clang-13)	7m 40s
posix (clang, clang++-14, 14,17,20, ubuntu-22.04, clang-14)	7m 49s
posix (clang, clang++-14, 14-gnu,17-gnu,20-gnu, ubuntu-22.04, clang-14)	8m 2s
posix (clang, clang++-15, 14,17,20, ubuntu-22.04, clang-15, deb http://apt.llvm.org/jammy/ llvm-t...	7m 41s
posix (clang, clang++-16, 14,17,20, ubuntu-22.04, clang-16, deb http://apt.llvm.org/jammy/ llvm-t...	7m 47s
posix (clang, clang++-17, 14,17,20, ubuntu-22.04, clang-17, deb http://apt.llvm.org/jammy/ llvm-t...	7m 46s
posix (clang, clang++-18, 14,17,20,23, ubuntu-24.04, clang-18, deb http://apt.llvm.org/noble/ llv...	10m 10s
posix (clang, clang++-19, 14,17,20,23, ubuntu-24.04, clang-19, deb http://apt.llvm.org/noble/ llv...	10m 3s
	1h 14m 50s

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