Fix RAM usage by splitting deeply nested expressions #3025

Job	Run time
duplicates	3s
spell_check	10s
build_system	24s
build (gcc-15.deb, --test-libcore)	17m 20s
build (gcc-15.deb, --extended-regex-example-tests)	6m 41s
build (gcc-15.deb, --extended-regex-tests)	11m 47s
build (gcc-15.deb, --extended-rand-tests)	9m 52s
build (gcc-15-without-int128.deb, --test-successful-rustc --nb-parts 2 --current-part 0)	13m 56s
build (gcc-15.deb, --std-tests)	7m 8s
build (gcc-15-without-int128.deb, --extended-regex-tests)	13m 28s
build (gcc-15-without-int128.deb, --extended-regex-example-tests)	7m 53s
build (gcc-15.deb, --test-successful-rustc --nb-parts 2 --current-part 1)	14m 11s
build (gcc-15-without-int128.deb, --extended-rand-tests)	9m 56s
build (gcc-15-without-int128.deb, --projects)	11m 50s
build (gcc-15-without-int128.deb, --std-tests)	8m 1s
build (gcc-15-without-int128.deb, --test-libcore)	17m 35s
build (gcc-15.deb, --test-successful-rustc --nb-parts 2 --current-part 0)	14m 24s
build (gcc-15-without-int128.deb, --test-successful-rustc --nb-parts 2 --current-part 1)	15m 38s
build (gcc-15.deb, --projects)	12m 52s
success	4s
	3h 13m 13s

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