Remove the use of floating-point for palette packing #4028

Job	Run time
macos-static	2m 20s
windows (32, windows-2019)	4m 45s
unix (ubuntu-20.04, g++, make)	5m 29s
windows (32, windows-2022)	5m 50s
unix (ubuntu-20.04, g++, cmake)	5m 25s
windows (64, windows-2019)	5m 29s
windows-mingw-build (32)	1m 35s
unix (ubuntu-20.04, clang++, make)	5m 48s
windows (64, windows-2022)	4m 16s
windows-mingw-build (64)	1m 0s
unix (ubuntu-20.04, clang++, cmake)	5m 53s
unix (ubuntu-22.04, g++, make)	6m 10s
unix (ubuntu-22.04, g++, cmake)	5m 52s
unix (ubuntu-22.04, clang++, make)	3m 59s
unix (ubuntu-22.04, clang++, cmake)	3m 56s
unix (macos-14, clang++, make)	7m 11s
unix (macos-14, clang++, cmake)	6m 57s
windows-mingw-testing (windows-2019, 32)	4m 4s
windows-mingw-testing (windows-2019, 64)	4m 3s
windows-mingw-testing (windows-2022, 32)	4m 38s
windows-mingw-testing (windows-2022, 64)	4m 23s
	1h 39m 3s

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