Changes to constant handling - faster deduplication, more compact represtntation #2643

Job	Run time
build_system	23s
duplicates	3s
build (gcc-15.deb, --test-libcore)	14m 40s
build (gcc-15.deb, --std-tests)	5m 54s
build (gcc-15.deb, --extended-rand-tests)	8m 22s
build (gcc-15.deb, --extended-regex-example-tests)	6m 28s
build (gcc-15.deb, --test-successful-rustc --nb-parts 2 --current-part 1)	11m 43s
build (gcc-15-without-int128.deb, --extended-regex-example-tests)	6m 10s
build (gcc-15.deb, --extended-regex-tests)	11m 48s
build (gcc-15-without-int128.deb, --test-libcore)	14m 45s
build (gcc-15-without-int128.deb, --extended-rand-tests)	8m 19s
build (gcc-15.deb, --test-successful-rustc --nb-parts 2 --current-part 0)	11m 59s
build (gcc-15-without-int128.deb, --test-successful-rustc --nb-parts 2 --current-part 0)	11m 39s
build (gcc-15-without-int128.deb, --std-tests)	5m 46s
build (gcc-15.deb, --projects)	11m 17s
build (gcc-15-without-int128.deb, --extended-regex-tests)	12m 28s
build (gcc-15-without-int128.deb, --test-successful-rustc --nb-parts 2 --current-part 1)	11m 47s
build (gcc-15-without-int128.deb, --projects)	10m 49s
success	2s
	2h 44m 22s

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