Move hexdec & dechex builtins to runtime-common (#1181) #435

Job	Run time
jammy/g++/c++17/asan=off/ubsan=off	7m 9s
focal/clang++/c++17/asan=off/ubsan=on	6m 24s
focal/g++-10/c++20/asan=on/ubsan=off	8m 2s
	21m 35s

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