Cleaned up tests by bringing objects under `mini_core` into scope #2530

Job	Run time
duplicates	2s
build (gcc-15.deb, --std-tests)	6m 14s
build (gcc-15.deb, --test-libcore)	14m 18s
build (gcc-15.deb, --extended-rand-tests)	8m 30s
build (gcc-15.deb, --extended-regex-example-tests)	6m 29s
build_system	25s
build (gcc-15.deb, --extended-regex-tests)	11m 34s
build (gcc-15.deb, --test-successful-rustc --nb-parts 2 --current-part 0)	11m 34s
build (gcc-15.deb, --test-successful-rustc --nb-parts 2 --current-part 1)	11m 18s
build (gcc-15.deb, --projects)	11m 34s
build (gcc-15-without-int128.deb, --std-tests)	6m 3s
build (gcc-15-without-int128.deb, --test-libcore)	14m 37s
build (gcc-15-without-int128.deb, --extended-rand-tests)	10m 2s
build (gcc-15-without-int128.deb, --extended-regex-example-tests)	7m 11s
build (gcc-15-without-int128.deb, --extended-regex-tests)	12m 9s
build (gcc-15-without-int128.deb, --test-successful-rustc --nb-parts 2 --current-part 0)	11m 27s
build (gcc-15-without-int128.deb, --test-successful-rustc --nb-parts 2 --current-part 1)	11m 23s
build (gcc-15-without-int128.deb, --projects)	11m 47s
success	1s
	2h 46m 38s

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